Precision rail guides

Transcription

1 Precision rail guides

2 Contents SKF the knowledge engineering company General information Introduction Features and benefits Product overview ACS in general SKF precision rail guides in kit packaging Technical data Materials Coating Permissible operating temperatures Permissible speed and acceleration Permissible minimum load Permissible maximum load Friction General rigidity behaviour Precision classes of rails Precision of rolling elements Dimensional accuracy Grading Jointed rails Dimensioning of precision rail guide systems The concept of static safety factor calculation The method of static safety factor calculation Rating life Rating life calculation Service life Cross reference to related chapters Determination of effective load ratings Static and dynamic load ratings given in the catalogue Influence of hardness Influence of operating temperature Rail guide arrangements Rail guide kinematics Number of rolling elements z, z T General geometry of a rail guide system Calculation of bearing loads Transfer of external loads to F y, F z, M x, M y, M z Preload force Transfer of F y, F z, M x, M y, M z to one load Influence of stroke length on equivalent dynamic load rating Equivalent dynamic mean load Maximum resulting load Elaborated equation for the static safety factor Elaborated equation for the rating life Example dimensioning calculation Rigidity calculation Determination of elastic deformation using the nomogram Determination of resulting deflection of a rail guide system Calculation example for the resulting deflection Technical data of precision rail guides with slide coating Surface pressure Wear Frictional properties Temperature range Chemical and humidity resistance Legend Product data LWR / LWRB LWRE LWRE ACS LWRE / LWRB ACSM LWRM / LWRV LWM / LWV LWM / LWV ACSZ LWRPM / LWRPV Other products LWML / LWV LWN / LWO LWJ / LWS flat rail guides GCL / GCLA standard slides LZM miniature slide... 86

3 3 Recommendations Design rules Designated use Typical mounting clamped arrangement Accuracy of mounting surfaces End pieces logic Chamfers on the precision rail guides Tolerance of distance between mounting holes Calculation of J 1 dimension Special mounting screws LWGD Preloading Tightening torques for mounting screws Mounting Important requirements General mounting rules Mounting of rail guides without Anti-Creeping System Mounting of rail guides with Anti-Creeping System Maintenance Lubrication Relubrication interval Repairs Stationary conditions / shipping / storage Ordering code Specification sheet

4 SKF the knowledge engineering company From one simple but inspired solution to a misalignment problem in a textile mill in Sweden, and fifteen employees in 1907, SKF has grown to become a global industrial knowledge leader. Over the years, we have built on our expertise in bearings, extending it to seals, mechatronics, services and lubrication systems. Our knowledge network includes employees, distributor partners, offices in more than 130 countries, and a growing number of SKF Solution Factory sites around the world. Research and development We have hands-on experience in over forty industries based on our employees knowledge of real life conditions. In addition, our world-leading experts and university partners pioneer advanced theoretical research and development in areas including tribology, condition monitoring, asset management and bearing life theory. Our ongoing commitment to research and devel opment helps us keep our customers at the forefront of their industries. Meeting the toughest challenges Our network of knowledge and experience, along with our understanding of how our core technologies can be combined, helps us create innovative solutions that meet the toughest of challenges. We work closely with our customers throughout the asset life cycle, helping them to profitably and responsibly grow their businesses. Working for a sustainable future Since 2005, SKF has worked to reduce the negative environmental impact from our operations and those of our suppliers. Our continuing technology development resulted in the introduction of the SKF BeyondZero portfolio of products and services which improve efficiency and reduce energy losses, as well as enable new technol ogies harnessing wind, solar and ocean power. This combined approach helps reduce the en viron mental impact both in our oper ations and our customers oper ations. SKF Solution Factory makes SKF knowledge and manu facturing expertise available locally to provide unique solutions and services to our customers. Working with SKF IT and logistics systems and application experts, SKF Authorized Distributors deliver a valuable mix of product and application knowledge to customers worldwide. 4

5 Our knowledge your success SKF Life Cycle Management is how we combine our technology platforms and advanced ser vices, and apply them at each stage of the asset life cycle, to help our customers to be more success ful, sustainable and profitable. Specification Maintain and repair Design and develop SKF Life Cycle Management Operate and monitor Manufacture and test Install and commission Working closely with you Our objective is to help our customers improve productivity, minimize main tenance, achieve higher energy and resource efficiency, and optimize designs for long service life and reliability. Innovative solutions Whether the application is linear or rotary or a combination, SKF engineers can work with you at each stage of the asset life cycle to improve machine performance by looking at the entire application. This approach doesn t just focus on individual components like bearings or seals. It looks at the whole application to see how each com po nent interacts with each other. Design optimization and verification SKF can work with you to optimize current or new designs with proprietary 3-D modell ing software that can also be used as a virtual test rig to confirm the integrity of the design. Bearings SKF is the world leader in the design, development and manufacture of high performance rolling bearings, plain bearings, bearing units and housings. Machinery maintenance Condition monitoring technologies and maintenance services from SKF can help minimize unplanned downtime, improve operational efficiency and reduce maintenance costs. Sealing solutions SKF offers standard seals and custom engineered sealing solutions to increase uptime, improve machine reliability, reduce friction and power losses, and extend lubricant life. Mechatronics SKF fly-by-wire systems for aircraft and drive-bywire systems for off-road, agricultural and forklift applications replace heavy, grease or oil consuming mechanical and hydraulic systems. Lubrication solutions From specialized lubricants to state-of-the-art lubrication systems and lubrication management ser vices, lubrication solutions from SKF can help to reduce lubrication related downtime and lubricant consumption. Actuation and motion control With a wide assortment of products from actuators and ball screws to profile rail guides SKF can work with you to solve your most pressing linear system challenges. 5

6 1 General information 1.1 Introduction As the world s leading rolling bearing manufacturer, SKF supplies practically every type of bearing for rotational and linear motion. SKF is therefore in a position, both technically and economically, to meet almost any customer requirement. This catalogue covers the entire range of SKF precision rail guides and accessories. SKF precision rail guides are highly accurate products for linear motion and are ideally suited for use in a wide variety of machine tools, machining centres, handling systems and special machinery, as well as in measuring and testing equipment and semi-conductor production machines. SKF precision rail guides are available in many different designs, sizes and standard lengths and which incorporate ball, roller or needle roller assemblies and slide coatings. They are supplied with the required accessories for attachment and sealing. The use of SKF precision rail guides enables the construction of economical, clearance-free linear guides of almost any type and length, according to the building block principle. The characteristics of the precision rail guides include: If cage creeping is likely, in particular when the guide is mounted vertically, precision rail guides with anti-creeping systems (ACS) are an obvious choice, as they will eliminate this problem. They are available for nearly all types of rolling elements. For applications characterised by high accelerations or short strokes of high frequency, SKF rail guides with slide coating are recommended. These rail guides are also suitable for machine tool applications where the damping properties of the guides are of greater importance than is the lower friction of rolling element rail guides. For those applications where precision rail guides are unsuitable, for instance because of their limited travel, SKF can supply alternative forms of linear guidance systems, like profile rail guides or linear ball bearings. All fast-selling precision rail guides are also available in convenient kit packaging. This ensures the complete delivery of all components including end pieces and screws in one package from stock. This catalogue brings together all the basic data that we believe will be of interest to customers. For further specialised advice, please contact your nearest SKF sales office. A constant, high degree of running accuracy. Low-friction, stick-slip free operation. High speed of travel. Low heat generation. Low wear and high reliability. High rigidity. Excellent load carrying capacity. 6

7 1.2 Features and benefits 1 Cage creep test results Axial displacement [mm] without anti-creeping system with anti-creeping system Anti-creeping system SKF developed the industry s first anti-cage-creep solution. It keeps the movement of the cage in the required position at the loaded zone, avoids cage creep from high operational speed and acceleration to uneven load distribution and weak adjacent parts, and prevents unplanned downtime and additional maintenance. In addition, due to defined cage position, SKF precision rail guides with anti-creeping system, or ACS, enable increased accuracy, higher accelerations (tested up to 160 m/s 2 ), and reliable vertical installation Distance travelled [km] Higher load rating and rigidity Compared to conventional LWR precision rail guides, SKF optimized the internal geometry and developed LWRE precision rail guides for applications that demand robust performance. Part of our modular range, LWRE precision rail guides feature rollers with a 33% larger diameter and utilize the entire roller length than those in LWR rail guides. These LWRE design upgrades fivefolded the load ratings and doubled the rigidity vs. LWR rail guides. In operation, the increased load rating and rigidity helps to increase process stability and reliability, ultimately extending equipment service life and reducing total cost of ownership. Permissible deviation in parallelism between reference surfaces and raceways Deviation in parallelism [µm] P10 P5 P2 Extreme accuracy and positioning repeatability Compared to other linear guiding products, precision rail guides provide the highest linear guiding accuracy. Precision rail guides from SKF are available in three different precision classes to meet a range of requirements for precision. The increased accuracy and repeatability enables higher productivity and product quality in diverse applications, e.g. semi-conductors, machine tools, measurement and testing equipment, and medical equipment Rail length [mm] A B Modular range With the SKF modular range of precision rail guides, outer rail dimensions remain the same, but rolling elements are interchangeable to best meet application demands. With this design modularity, customers can easily increase load rating or extend rating life without having to redesign the equipment. The SKF modular range of precision rail guides covers 80% of dimensions on the market. Additionally, the customer can chose between ball assemblies, crossed roller assemblies, crossed roller assemblies with ACS/ ACSM, needle roller assemblies and slide coatings. 7

8 1.3 Product overview 8

9 SKF can offer a large assortment of precision rail guides ( table 1). The different versions, mainly characterized by their type of rolling elements, are as follows: Ball assemblies of LWRB series. Ball assemblies with Anti-Creeping System of LWRB ACSM series. Crossed roller assemblies of standard LWR series. The following table shows the complete range of SKF precision rail guides, together with all available sizes. The blue shaded areas indicate the sizes included in the Modular Range. Contrary to the current lack of uniformity within the market, the interchangeable precision rail guides of the Modular Range are all within the same outer dimensions ( fig. 1). For fast delivery, please refer to the rail guides that are available in kit packaging. Fig. 1 1 Crossed roller assemblies of optimised LWRE series. Crossed roller assemblies with Anti- Creeping System of LWRE ACS series. Crossed roller assemblies with Anti- Creeping System of LWRE ACSM series. Needle roller assemblies of LWRM/LWRV series. Needle roller assemblies of LWM/LWV series. Needle roller assemblies with Anti-Creeping System of LWM/LWV ACSZ series. Market situation Slide coating of LWRPM/LWRPV series. SKF modular range Table 1 Product overview Type B A Size (A B mm) , LWRB X X LWRB ACSM L LWR X X X L LWRE X L X X X LWRE ACS X L L X L LWRE ACSM X L L X L LWRM / V X X LWM / V X X X L L L LWM / V ACSZ L L L L L L LWRPM / V X X X X = Prompt delivery in standard lengths (see specific product tables) L = Delivery time on request = Not available = Modular range 9

10 1.4 ACS in general Many users are familiar with cage-creeping in conventional precision rail guides. This occurs when the cage moves out of its intended position, adversely affecting performance and possibly requiring service. This effect may occur, for example, as a result of high acceleration, uneven load distribution or vertical mounting. SKF has solved this problem by offering highly sophisticated Anti-Creeping Systems (ACS) for most guiding types. Advantages: Cage-creeping eliminated. Suitable for high acceleration, vertical mounting and uneven load distribution. Increased accuracy due to defined position of the cage. Easily interchangeable with standard precision rail guides because they have identical dimensions. Less downtime and maintenance. LWRE with ACS LWRE with ACSM LWRE with ACS The original anti-creeping system for all types of LWRE rail guides. LWRE with ACSM Refinement of our own ACS solution led to version ACSM for LWRE rail guides with a maximum length of 400 mm. The cage, with an involute-toothed control gear made of brass, and involute teeth directly machined into the rail, are especially suitable for high accelerations. LWM / LWV with ACSZ For precision rail guides with needle roller cages, SKF can offer version ACSZ. Both rails are equipped with gear racks made of steel. The cage carries two steel control gears that help to ensure the correct cage position. LWM / LWV with ACSZ 10

11 Rails for anti-creeping cages Fig. 2 Rails for ACS- or ACSZ-cages can be designed for a specified stroke or maximum stroke, with the length of the toothing in the rail varied accordingly ( fig. 2 and 3). Rails for ACSM-cages are always made for maximum stroke. A rail for maximum stroke has teeth along its entire length. This may be required for mounting, maintenance or dismounting purposes. Rails for ACS- or ACSZ-cages are delivered with maximum stroke as standard and no special ordering code is required. For rails with a specified stroke, the length of the stroke, which is symmetrical to the rail, must be stated in millimetres after the suffix ACS / ACSZ. ACS- and ACSZ-cages must be operated only along the specified stroke length to ensure that the control gear is not damaged. Ordering example maximum stroke: 4x LWRE 6500 ACS 2x LWAKE 6x30 ACS 8x LWERE 6 LWRE ACS standard stroke LWRE ACS specified stroke Fig. 3 1 Ordering example specified stroke of 340 mm: 4x LWRE 6500 ACS 340 2x LWAKE 6x30 ACS 8x LWERE 6 Ordering example kit packaging: LWRE 6200 ACSM-KIT 11

12 1.5 SKF precision rail guides in kit packaging To simplify the ordering process and warehousing for our customers, SKF offers precision rail guides in pre-defined kits. Each kit consists of 4 rails in precision class P10, 2 cages and 8 end pieces (ACSM kits without end pieces). The available kits can be found in the specific rail guide chapters. On request it is possible to order a kit with two rails in standard length and two short rails with lead in radius. Additionally the number of rolling elements can be varied, see ordering code. Completely customised precision rail guide sets are also possible on request. Advantages of rail guide kits All components required are supplied ready-to-mount and can be ordered with a single order number. Most kits are available from stock. Cage length is easily adjustable. 1) Load capacities are already calculated for the kit. 2) Available with ACS or ACSM for effective prevention of cage-creeping. Rails for ACS- or ACSM-cages with toothing along entire length (rails for maximum stroke). 1) Do not cut the cage shorter than 2/3 of the total rail length. 2) Load capacities are given for a kit of 4 rails and 2 cages in clamped arrangement (C 0eff slide, C eff slide) 12

13 1.6 Technical data Permissible operating temperatures Permissible minimum load Materials As standard, precision rails are manufactured from tool steel 90MnCrV8 (1.2842) with a hardness between 58 and 62 HRC. However, if required by the application, the rails can also be supplied in stainless steel, e.g. X90CrMoV18 (1.4112). All rails from the LWRE ACSM series are made of stainless steel X46Cr13 (1.4034) or X65Cr13 (1.4037). Standard rolling elements are made from carbon chromium steel 100Cr6 (1.3505) with a hardness between 58 and 65 HRC. Stainless steel rolling elements are available on request. The cages of SKF rolling element assemblies are manufactured from hard plastic or aluminium. The material of LWAKE crossed roller units is POM, and for all other rolling element assemblies, PA 12 or equivalent, sometimes reinforced with glass fibres. Aluminium cages are made of AlMgSi0,5 (EN AW-6060). For other cage materials such as Peek, steel, brass, etc., please contact SKF. Standard end pieces are made of blackened steel. Additionally, the standard end pieces can be supplied as chromed end pieces when ordered with suffix /HV Coating For corrosive environments, the rails can be protected with a special TDC (Thin Dense Chrome) coating. This coating, with a layer hardness of 900 to 1300 HV, substantially improves corrosion resistance and thus increases wear resistance under critical operating conditions. The salt spray test, which complies with DIN EN ISO 9227, resulted in 72h corrosion protection. The coating is matt grey in colour and complies with RoHs requirements. The load capacity is not affected by the coating. Due to the electrolytic process, the mounting holes and other grooves or drills might not be fully coated. The suffix for ordering is / HD. The range of operating temperature for SKF precision rail guides depends largely on the particular cage type used. Guides with metal cages and end pieces without wipers can generally be used up to +120 C. For rail guides with plastic components, the operating temperature range is 30 C to +80 C. Please note that the temperature limit of the used lubricant must also be taken into account. Permanently higher operating temperatures for precision rail guides without plastic components are possible but the hardness of the material and thus the load carrying capacity will decrease. The detailed explanation of the influence of higher temperatures on the load carrying capacity (factor f t ) can be found in chapter The accuracy of the rail guide worsens with increasing temperature due to changes in the material structure and dimensional changes Permissible speed and acceleration SKF precision rail guides that are correctly mounted and preloaded, can be used for running speeds up to 2 m/s and accelerations up to 25 m/s 2. Needle roller cages can be accelerated with maximum 100 m/s 2. For cages with ACSM, the maximum acceleration is 160 m/s 2 and for cages with ACSZ the value is 100 m/s 2. Higher running speeds and accelerations are possible, depending on bearing design, bearing size, applied load, lubricant and bearing preload. In such instances, please consult SKF. To prevent the rolling elements from sliding on the raceway during operation at higher speeds or high acceleration, the precision rail guide system must be loaded at all times with a minimum 2% of the dynamic load rating. This is particularly important for applications characterized by highly dynamic cycles. Precision rail guide systems preloaded according to the table, Tightening torques of set screws ( chapter ), are typically able to satisfy the stated minimum load requirements Permissible maximum load ISO Part 1 stipulates that calculation of bearing life is valid only when the equivalent dynamic mean load P m of a precision rail guide does not exceed 50% of the dynamic load rating C. Any higher loading leads to an imbalance of stress distribution, which can have a negative impact on bearing life. As stated in ISO Part 2, the maximum load should not exceed 50% of the static load rating C Friction Friction in a precision rail guide with rolling elements depends not only on the loading, but on a number of other factors, notably the type and size of the bearing, the operating speed, and the properties of the lubricant. The cumulative running resistance of a rail guide is composed of the rolling and sliding friction at the contact zone of the rolling elements, friction at the points of sliding contact between the rolling elements and cage, churning work within the lubricant and friction from the seals or wipers. The coefficients of friction under normal operating conditions, with grease lubrication and good mounting accuracy, are between 0,0005 and 0,004. For rail guides fitted with wipers, the coefficient of friction and the starting friction is significantly higher due to the friction of the wipers themselves. 13

14 1.6.8 General rigidity behaviour General rigidity behaviour of different rolling elements Diagram 3 The rigidity of a precision rail guide (expressed in N/µm) is defined as the ratio between the acting external load and the elastic deflection resulting in the rail guide. Besides the load carrying capacity, rigidity is one of the most important selection criteria for a precision rail guide system. The elastic deflection of a system depends on the magnitude and direction of the external load, the preload, the type of rail guide including size and cage length, and the mechanical properties of the adjacent support structure, including screws and joints between components. On a preloaded rail guide system the deflection under load within a given load range will be less than for a rail guide without preload. Variations in contact geometry are the main factors contributing to the general rigidity behaviour of the cage types ( diagram 3). The details are explained in chapter Precision classes of rails In order to meet the precision requirements of rail guide systems, SKF produces rails in three different precision classes. These are classified according to the parallelism between the raceways and reference surfaces A, (as indicated, on the reverse side of the SKF label), and B. See table 2 and fig. 4. Tolerance t of parallelism to reference surfaces Table 2 Rail length Precision class > P10 P5 P2 mm µm P10 This is the standard precision class and meets the requirements of general machinery. The tolerance of parallelism for a mm long rail is maximum 9 µm. P5 Deflection [µm] Precision class P5 satisfies the demands normally made on the running accuracy for machine tool applications. The tolerance of parallelism for a mm long rail is 5 µm maximum. P2 External load [N] LWRB + LWRB LWR + LWR LWRE + LWRE LWRV + LWRM Precision class P2 is for the most exacting demands. Rails made to this precision class should only be used when the associated components are manufactured to a correspondingly high degree of precision. Rails of precision class P2 will be manufactured by SKF to special order. If the requisite accuracy on the order is not specified, rails with standard P10 tolerances will be supplied. Fig ) t B t A A B t B t A A B 1) Rail length > mm, please contact SKF 14

15 Precision of rolling elements The rolling elements used in precision rail guide cages are of very high quality and have a specification according to table 3. Besides the standard type, needle roller cages can be delivered in class G1, when ordered with suffix /G Dimensional accuracy SKF precision rail guides are produced with the following tolerances ( fig 5): Width A: +0 / 0,3 mm Height B: +0 / 0,2 mm Centre Height H1 = H2: ± 5 µm 1) Assembly Height T = H1 + H2: ± 10 µm 1) Precision of rolling elements Rolling element Norm Class Roundness Sorting Comment µm µm Balls DIN G10 0,25 1 Standard Cylinder roller DIN G1 0,5 1 Standard Needle roller DIN G2 1 2 Standard Not mentioned in DIN G1 0,5 1 Suffix /G1 Table 3 Fig. 5 1 Rail length Lrail: L rail 300: ± 0,3 mm L rail > 300: ± 0,001 mm L rail H 1 A Grading For the typical clamped arrangement, four precision rail guides are needed. To reach the best performance in terms of lifetime, rigidity and running behaviour, it is important that the centre height of the four rails is within a small tolerance. This is the reason why SKF rails are graded and packed together according following rules: T B H 2 Rails for crossed roller or ball cages: Four rails are matched to each other and packaged as a set. Rails for needle roller cages or slide coatings: Two M shaped and two V shaped rails are matched and packaged as pairs. Because of the very close standard tolerance of the centre height, it would also be possible to pair any rail for a standard application (precision class P10) if necessary. 1) for rail length L rail < mm 15

16 Jointed rails Jointed rails are always graded and wellsorted by SKF to ensure smooth running. They are delivered with markings as indicated in fig. 6. For rails composed of two or more sections, the tolerance for the total length is ±2 mm. Fig A Set number Rail track Joint Set 1 1-1A 1-1A 1-1B 1-1B 1-2A 1-2A 1-2B 1-2B 1-3A 1-3A 1-3B 1-3B 1-4A 1-4A 1-4B 1-4B 16

17 1.7 Dimensioning of precision rail guide systems Often it is not possible to build a prototype machine just to find out which the most suitable guiding for a given application is. Instead, the following established and proven procedures are recommended: Calculation of rating life Calculation of static safety factor These two calculation methods must consider all loads and forces acting on the precision rail guide system. Representatives of the acting bearing load that describe the whole load case are needed. These representatives must combine all forces, leverarms and torque loads, which can vary by time or stroke ( chapter 1.9 and following). The rating life of a precision rail guide with rolling elements is defined as the total linear distance travelled by the rails before the first sign of material fatigue occurs on one of the raceways and/or the rolling elements. For the selection of rail guides based on rating life calculation ( chapter 1.7.3), the dynamic load rating C, as defined in chapter 1.8, is used. It is expressed as the load that results in a bearing life of m The concept of static safety factor calculation When selecting a precision rail guide, the static safety factor calculation must be considered when one of the following cases arises: The bearing operates under load at very low speeds. The bearing operates at normal conditions but must also accept heavy shock loads. The bearing is loaded stationary for long periods of time. The bearing is loaded with P > 50% of the dynamic load rating C where the theory of rating life calculation is not valid any more. In all such cases, the permissible load is determined not through material fatigue but through the permanent physical deformation at the contact zone of the rolling elements and raceways. Load applied when stationary or at very low operating speeds, as well as heavy shock loads, causes flattening of the rolling elements and results in damage to the raceways. The damage may be uneven or may be spaced along the raceway at intervals corresponding to the rolling element separation. This permanent deformation leads to vibration in the bearing, noisy running and increased friction and even may cause a decrease in preload and, in an advanced stage, an increase in clearance. With continued operation, this permanent deformation may become a starting point for fatigue damage due to resulting peak loads. The seriousness of these phenomena will depend on the particular bearing application The method of static safety factor calculation When determining the bearing size according to static load rating ( chapter 1.8), one must consider a certain relationship, known as the static safety factor s 0, between the static load rating C 0 and the maximum static load P 0. The static safety factor s 0 determines the degree of safety against excessive permanent deformation of the rolling elements and raceways. The static load rating, C 0, is defined as the static load that would produce a permanent deformation of 0,0001 times the rolling element diameter. Experience shows that, depending on the contact conditions, a maximum Hertzian pressure of MPa is permissible at the zone of maximum load without affecting the running qualities of the bearing. See also ISO Static safety factor depending on operating conditions Operating conditions s 0 Calculation of the static safety factor For a chosen precision rail guide and a defined load case, the static safety factor s 0 can be calculated by: C 0, eff slide C 0, eff slide s 0 = JJKKL = JJJLL P 0 F res max where s 0 = static safety factor C 0, eff slide = effective static load rating of a slide [N] P 0 = maximum static load [N] F res max = maximum resulting load [N] Based on practical experience, guideline values have been specified for the static safety factor s 0, which depend on the operating mode and other external factors ( table 4). If, for example, the precision rail guide system is exposed to external vibrations from machinery in close proximity, higher safety factors should be applied. Moreover, the load transfer paths between a precision rail guide system and its support structure should be taken into account. In particular, the screw connections must be examined for adequate safety. For overhead installations of precision rail guides, higher safety factors should be applied. Note: The general technical rules and standards in the respective industrial sector also must be observed. Table 4 Normal conditions > 1 2 Smooth, vibration-free operation > 2 4 Medium vibrations or impact loads 3 5 High vibrations or impact loads > 5 Overhead installations The general technical rules and standards in the respective industrial sector must be observed. If the application poses a risk of serious injury, the user must take appropriate design and safety measures that will prevent all rails from becoming detached from the base (e.g. due to loss of rolling elements or failure of screw connections). 17 1

18 Requisite static load rating For specific operating conditions with a related recommended static safety factor and a defined load case, the requisite static load rating C 0 can be calculated from the following formula: C 0, eff slide = s 0 P 0 = s 0 F res max where C 0, eff slide = effective static load rating of a slide [N] P 0 = maximum static load [N] s 0 = static safety factor = maximum resulting load [N] F res max Rating life In laboratory tests and in practice it is found that the rating life of apparently similar bearings under completely identical running conditions can differ. Therefore, calculation of the appropriate bearing size requires a full understanding of the concept of bearing rating life. All references to the dynamic load rating of SKF precision rail guides apply to the basic rating life, as covered by the ISO definition (ISO ), in which the rating life is understood as the life reached or exceeded by 90% of a large group of identical bearings. The majority of the bearings reach a longer rating life, and half the total number of bearings reach at least five times the basic rating life Rating life calculation The rating life of precision rail guides expressed in km, L ns, can be calculated using the following formula: C eff slide = effective dynamic load rating of a slide [N] P = equivalent dynamic load [N] p = life exponent; p = 3 for balls, p = 10/3 for rollers n = stroke frequency [double strokes/min] S = single stroke length [mm] Note: The concept of rating life calculation is only valid in cases where the equivalent dynamic load P does not exceed 50% of the dynamic load rating C. See also the indication for static calculation in chapter Note: The life of a precision rail guide can be calculated to a degree of precision and reliability governed by the accuracy of the information about the load case and the known or calculable operating conditions. Note: Lifetime calculation is related to the physical effect of fatigue of material. Fatigue is the result of shear stresses cyclically appearing immediately below the load carrying surface. After a time, these stresses cause cracks that gradually extend up to the surface. As the rolling elements pass over the crack, fragments of material break away. This process is known as flaking or spalling. The flaking progressively increases and eventually makes the bearing unserviceable. Factor c 1 for reliability Factor c 1 is used in the calculation of bearing life in cases where the intended prediction of reliability has to exceed 90%. The corresponding values for c 1 are given in table Service life In addition to rating life, there also exists the concept of service life. This term describes the period of time for which a given linear bearing remains operational in a given set of operating conditions. Therefore, the service life of the bearing depends not necessarily on fatigue but also on wear, corrosion, failure of seals, lubrication intervals (grease life), misalignment between the rails, vibration during standstill, etc. Normally, the service life only can be quantified in tests under realistic operating conditions or by comparison with similar applications Cross reference to related chapters For the two dimensioning concepts presented in this chapter, static safety factor and basic rating life, the following input data is needed: The loads acting on the precision rail guide system. Their calculation will be explained in detail in chapter 1.9. The effective static and dynamic load rating of a certain precision rail guide system. Their calculation will be presented in the next chapter. q C eff slide w p L ns = c JJKK < P z In load cases where the length of travel and stroke frequency is constant, it is often more useful to calculate the rating lives in operating hours L nh using formula 4: q C eff slide w p L nh = c 1 JKKK JJKK S n 60 < P z Factor c 1 for reliability Reliability % L ns c 1 90 L 10s 1 95 L 5S 0,62 96 L 4s 0,53 97 L 3s 0,44 98 L 2s 0,33 99 L 1s 0,21 Table 5 where L ns L nh c 1 = modified basic rating life [km] = modified basic rating life [h] = factor for reliability 18

19 1.8 Determination of effective load ratings For a slide equipped with four precision rails and two rolling element assemblies with an individual number of rolling elements ( fig. 11), the effective static and dynamic load rating are calculated by: Fig. 7 1 z T 2 C 0, eff slide = f h0 f t C 0,10 JJL 10 f 1 q z T 2 w w C eff slide = f h f t C 10 JJL < 10 f 1 z where C 0, eff slide = effective static load rating of a slide [N] C 0,10 = basic static load rating of a rail guide with specified number of rolling elements [N] f h0 = factor for hardness, static f t = factor for operating temperature z T = number of load carrying rolling elements (per cage or per row for needle rollers) = factor for load direction f 1 C eff slide = effective dynamic load rating of a slide [N] C 10 = basic dynamic load rating of a rail guide with specified number of rolling elements [N] f h = factor for hardness, dynamic w = rolling element exponent; w = 0,7 for balls, w = 7/9 for rollers Fig. 8 Fig Static and dynamic load ratings given in the catalogue The basic load ratings C 10 and C 0,10 quoted in the product data tables of rolling element assemblies are defined for one rail guide loaded in the direction shown in fig. 7 and the following amount of rolling elements: Fig. 10 For 10 balls under load ( fig. 8) For 10 crossed rollers under load ( fig. 9) For 20 needle rollers under load (2 10 needle rollers per row) ( fig. 10)

20 1.8.2 Influence of hardness The full load rating of the rolling element assembly can be utilized completely (both factors equal 1) only if the surface hardness of the raceways is at least 58 HRC. If rails of stainless or acid-resistant steel are used and their raceway hardness doesn t reach the required limit, the values for the factors f h and f h0 can be obtained from diagram 4. If rolling elements with a lower hardness, e.g. made from stainless steel, are used, the same factor has to be considered. Factor f h for the influence of hardness f h 1 0,8 0,6 0,4 0,2 f h0 f h Diagram 4 Note: The static and dynamic load ratings for rolling element assemblies with ACSM, given in the product tables, already are reduced. The corresponding rails are made from stainless steel by standard. For this speciality, it is not useful to additionally utilize the factors f h0 < 1 and f h < Influence of operating temperature When a precision rail guide without plastic cage is permanently used with operating temperatures above +120 C, the load ratings will decrease by a certain amount. In such cases, the temperature factor f t has to be taken into consideration. Values of factor f t can be obtained from diagram 5 as a function of the operating temperature HRC Diagram 5 Factor f t for the influence of operating temperature f t 1 0,8 0,6 0,4 0, Operating temperature [ C] 20

21 1.8.4 Rail guide arrangements Fig Precision rail guides can be mounted in several types of arrangements, to suit the requirements of the particular application. Two of these are described below. The impact of the two types of arrangements on the load ratings is expressed in factor f 1 for load direction ( fig. 11). Clamped arrangement f 1 = 2 Clamped arrangement The most common way to design a precision rail guide system is the clamped arrangement, as it has several advantages: The rails can be preloaded to meet demands for rigidity and running accuracy. The system can accommodate loads and moments in any direction. It has a small cross section for compact construction. Floating arrangement f 1 = 1 As a rule, rail guide systems in clamped arrangements consist of two identical precision rail guides, as shown in fig. 11. With rail guides in such an arrangement, it is even possible to adjust the preload, such as by using set screws, as explained in chapter Floating arrangement A rail guide system in a floating arrangement consists of a locating bearing e.g. a LWR rail guide, which provides guidance in the longitudinal and lateral directions, and another rail guide with two flat raceways, which acts as the non-locating bearing ( fig. 11). In such arrangements, care should be taken to ensure that both guide systems are of similar load rating and rigidity. Rail guide systems in floating arrangement are able to take up loads that are predominantly vertical only. However, they can support heavy loads and are simple to mount. They can be used to advantage where: Thermal expansion must be compensated Large distances between supports have to be bridged Rail guide kinematics Depending on the application, considering the available space, stroke and environmental conditions, precision rail guide systems can be designed in different ways. Possible kinematics and their individual characteristics are described in the next chapters. When selecting the dimension of a rail guide and rolling element assembly, the requirements regarding geometry and installation space or the requirements regarding load rating and rigidity are of primary importance. In the first case, the maximum applicable cage length is calculated depending on stroke and length of the rails. The given equations are transformed, if load capacity or rigidity requirements determine the length of the cage. In this case, the length of the rails is calculated depending on the length of the cage and stroke. 21

22 Not overrunning systems without wipers Fig. 12 The rolling element assembly always moves half the distance travelled by the moving rail and remains between the rails ( fig. 12). In case the geometry is given L cage, max = L rail 0,5 S Middle position S/4 L rail L cage S/4 or the rating life / rigidity defined the length of the rolling element assembly L rail, min = L cage + 0,5 S where L cage, max = maximum length of rolling element assembly, if rail length and stroke are predefined [mm] L rail = length of the rail [mm] L rail, min = minimum length of the rail, if length of cage and stroke are predefined [mm] L cage = length of rolling element assembly [mm] S = intended stroke length [mm] S/4 Right end position Left end position S/2 S S/2 Precision rail guide system with wipers If the rail guide has to be sealed with wipers, it is important to ensure that the lips of the wipers seal against the raceway of the opposing rail over the whole length of travel. Normally, the rail guide arrange ment is fitted with two rails of different length. The wipers are attached to the shorter rail, of which the length is determined according to the formulas given above under heading Not overrunning systems without wipers. The minimum length of the long rail is ( fig. 13) S/2 + L 1 L rail S/2 + L 1 Fig. 13 L rail, long, min = L cage + 1,5 S + 2 L 1 or in case the geometry is given L cage L rail, long L cage, max = L rail, long 1,5 S 2 L 1 where L rail, long, min = minimum length of the long rail, if length of cage and stroke are predefined [mm] L cage = length of rolling element assembly [mm] L 1 = thickness of end piece with wiper [mm] L cage, max = maximum length of rolling element assembly, if rail length and stroke are predefined [mm] L rail, long = length of the long rail [mm] S = intended stroke length [mm] 22

23 Overrunning system without wipers Fig. 14 If a short precision rail moves on a long rail, overrunning rolling element assemblies should be preferred. It is important that the short rail has lead in radius at both rail ends (ordered with suffix EG ) so that the overrunning cage causes as little pulsation as possible. Not every cage is suitable for this application. The maximum cage overrun ( free length of the cage) depends on the orientation of the rails and on the cage material. In case of priority of installation space, the length of the components is calculated by ( fig. 14) S L rail, long L cage L rail, short 1 L cage, max = L rail, long 0,5 S and L rail, short = L rail, long S If rigidity or load rating are more important L rail, long = L cage + 0,5 S and L rail, short = L rail, long S where L cage, max = maximum length of rolling element assembly, if rail length and stroke are predefined [mm] L rail, long = length of the long rail [mm] L rail, short = length of the short rail in an overrunning system [mm] L cage = length of rolling element assembly [mm] S = intended stroke length [mm] 23

24 1.8.6 Number of rolling elements z, z T After the calculation of the maximum cage length L cage, max and the length of the rails according to demanded geometry, the number of rolling elements z has to be calculated for ordering the right length of rolling element assembly. Depending on the different kinematic types the number of load carrying elements z T has to be defined for the calculation of the rating life. The following overview shows the formulas for z and z T. For kinematic types, where the rolling element assembly always remains between the rails (not overrunning rail guide without wipers and rail guide with wipers) and all rolling elements carry load, z = z T is valid. In overrunning systems, only the rolling elements underneath the short rail can carry load, and z T has to be cal culated differently. The formulas are using the function truncate to get an integer number of rolling elements. With that, the real cage length for ordering L cage and the load carrying length L T, defined from the center of the first load carrying rolling element to the center of Not overrunning rail guide without wipers (Standard) L rail L cage Rail guide with wipers L rail Overrunning rail guide without wipers Lcage Lrail, short L cage L rail, long Lrail, long t 1 t t 2 t 3 Values for t, t 1, t 2 and t 3 for the different cage types are given in the chapter Product data if no value for t 2 is given: t 2 = t 1 if no value for t 3 is given: t 3 = 0 q L cage, max t 1 t 2 t 3 w z = TRUNC JJJJJJJLLL +1 < t z q L cage, max t 1 t 2 t 3 w z T = TRUNC JJJJJJJLL +1 < t z q L rail, short t 3 2 EG w z T = TRUNC JJJJJJJLLL +1 < t z L cage = (z 1) t + t 1 + t 2 + t 3 L T = (z T 1) t + t 3 L install = L rail + S + 2 L L install = L rail, long L install = L rail, long + 2 L Legend: z = number of rolling elements (per cage or per row for needles) z T = number of load carrying rolling elements (per cage or per row for needles) L cage = length of rolling element assembly [mm] L cage, max = maximum length of rolling element assembly [mm] L T = load carrying length [mm] L rail, short = length of the shorter rail in an overrunning system [mm] L rail, long = length of the long rail [mm] t = pitch of rolling elements in a cage [mm] t 1, t 2 = distance of outer rolling element to the end of cage [mm] t 3 = length of anti-creeping system [mm] EG = length of lead in radius on each side, typically 1 2 mm [mm] L install = length of the complete installation space [mm] L = thickness of the end piece [mm] Note: TRUNC is the mathematical function that truncates a number to an integer by removing the fractional part of the number. 24

25 the last, can be calculated. Additionally the formulas for the installation length L install are given. Fig General geometry of a rail guide system As a general recommendation, the length of a rolling element assembly can be chosen using the following guidelines: B 1 clamped arrangement floating arrangement L cage = S L cage = 1,5 S where L cage = length of rolling element assembly [mm] S = intended stroke length [mm] It should be remembered, however, that where loads are heavy, applied off-centre, or include torque loads, the longest possible rolling element assembly should be chosen to achieve both, an even load distribution and high rigidity. L T A further recommendation is that the mean distance between the rolling element assemblies B 1 should not exceed the loadcarrying length L T ( fig. 15): L T > B 1 where B 1 = mean distance between the rolling element assemblies [mm] L T = load carrying length [mm] 25

26 1.9 Calculation of bearing loads The load can be directly inserted into the rating life equations and the static safety factor equation, if the load F acting on a rail guide is constant in magnitude, position and direction and acts vertically and through the centre of the raceway. In all other cases, it is first necessary to calculate the maximum resulting load F res, max and the equivalent dynamic load P. These representative loads are defined as the loads that would have the same influence on the rating life and on the static safety factor s 0 as the real set of loads. How to deal with loads that are not vertically and not through the center of the rail guide system is described in chapter 1.9.1, and How to deal with time- or position-varying loads will be explained in chapter Transfer of external loads to F y, F z, M x, M y, M z First, the coordinate system for the selected layout has to be defined. It is preferred to define the moving direction as x-axis. The origin of the coordinate system is set to the middle of the rolling element assembly and all lever arms in x-direction are measured from there. This means, that the coordinate system moves and that lever arms change with the movement of the guiding ( fig. 16). In the other directions, the origin should be symmetrically between the rolling element assemblies at B 1 /2 and on the rails center height ( chapter ). Second, all working loads, that have impact on the rail guide system, have to be collected. Load directions and lever arms must not be ignored. The single external loads are summarized to a set of five values: F y, F z, M x, M y, M z. These five values are calculated by U F y = O F y,i i = 1 U F z = O F z,i i = 1 U M x = O F y,i z i +O F z,i y i i = 1 i = 1 U M y = O F x,i z i O F z,i x i i = 1 i = 1 U M z = O F x,i y i +O F y,i x i i = 1 i = 1 U U U where F x,i, F y,i, F z,i = single loads in x-, y- or z-direction that act simultaneously on the rail guide system [N] F y, F z, = summarized force (load) in y- or z-direction [N] M x, M y, M z = summarized torque load in x-, y- or z-direction [Nm] x i, y i, z i, = lever arms that are related to the single loads [m] i = counter for single loads in x-, y- or z-direction that act simultaneously U = amount of loads that act simultaneously Note: The given set of five values, F y, F z, M x, M y, M z, are independent of the concrete geometry of the rail guide system. The premise for the next calculation steps is that the type and length of rolling element assembly is chosen and the related characteristic values C, C 0 and L T are defined. Additionally, a value for the mean distance between rolling element assemblies, B 1, needs to be defined ( chapter 1.8.7). Fig. 16 +F z F z, i +z F y, i F x, i +F x +z z i +x +F y +y x i y i ORIGIN +x ORIGIN B 1 M y F x, drive z drive B 1 +A M x M z 26

27 1.9.2 Preload force The additional load generated by the preload in a clamped arrangement has to be considered during the dimensioning calculation. The factor for preload, f Pr, depends on the type of rolling element assembly. ( chapter 3.1.9). This so-called preload force is calculated by 1 F Pr = C eff f Pr C eff = C eff slide for clamped arrangement Where F Pr = preload force [N] C eff = effective dynamic load capacity for one rolling element assembly [N] f Pr = factor for preload, % Transfer of F y, F z, M x, M y, M z to one load The set of five load values F y,f z, M x, M y, M z are summed up to the combined bearing load q s M x s s M y s s M z s w F comb = sf y s +sf z s +s JJJLLL + JJJLLL + JJJLLL s < s B 1 s s L T s s L T s z The resulting load F res, that includes the preload force F Pr, is used for the static dimensioning. q s M x s s M y s s M z s w F res = F Pr + F comb = F Pr + sf y s +sf z s +s JJJLLL + JJJLLL + JJJLLL s < s B 1 s s L T s s L T s z The equivalent dynamic load P, that considers the factor for stoke length f s, is used for dynamic dimensioning. t s M x s s M y s s M z s P = f y s F res = f s s F Pr +s F y s +s F z s + JJJLLL + JJJLLL + JJJLLL s v s B s s 1 L T s s L T s b where F comb = combined bearing load F res = resulting load [N] F Pr = preload force [N] F y,, F z, = summarized force (load) in y- or z-direction [N] M x, M y, M z = summarized torque load in x-, y- or z-direction [Nm] B 1 = mean distance between the rolling element assemblies [mm] L T = load carrying length [mm] P = equivalent dynamic load [N] = factor for stroke length f s 27

28 1.9.4 Influence of stroke length on equivalent dynamic load rating Factor f s for the influence of stroke length Diagram 6 When defining the operating conditions for the calculation of the basic rating life, it is assumed that the reference stroke length for the precision rail guide is equal to the length of the rolling element assembly. In precision rail guide applications, however, this rarely applies. Exhaustive life tests have shown that there is a reduction in the life of a precision rail operated with a short stroke length. This influence of the stroke length in relation to the length of the rolling element assembly is shown in diagram 6. For ratios greater than 0,6, the reduction in rating life is insignificant, but for lower values, the factor f s modifies the equivalent dynamic load. In the case of values under 0,1, unfavourable tribological conditions render the calculation of bearing life impractical. Under such conditions, the rating life is determined largely by the sliding conditions in the contact zone. f s 2,5 2 1,5 1 0, ,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 Stroke length / Length of rolling element assembly Diagram 7 Variable load on a precision rail guide Equivalent dynamic mean load F res, P F res, max. P m The rating life calculation formulas are based on the assumption that the load and the speed are constant. In reality the external loads, positions and speeds are changing in most cases and the workflow has to be separated into load phases with constant or approximately constant conditions along their individual strokes. Since the lever arms in x-direction are changing with the movement of the guiding, the equivalent dynamic load is varying continuously and for calculations without electronical devices simplifications have to be made ( diagram 7). All single load phases are summarized to the equivalent dynamic mean load P m depending on their individual stroke length: 7 V p 7 Os Pj s Sj j=1 P m = p JJJJL S tot S tot = S 1 +S 2 + S S V S 1 where P m = equivalent dynamic mean load [N] P = equivalent dynamic load [N] p = life exponent; p = 3 for balls, p = 10/3 for rollers j = counter for load phases V = amount of load phases S j = individual stroke length [mm] S tot = total stroke length [mm] Note: The distance to the reversal points is relevant for the determination of the factor f s. Sequenced load phases with identical moving direction deliver one complete stroke length. S 2 S 3 S v S tot Maximum resulting load The maximum value of F res is required for calculating the static safety factor s 0. To this end, all loads must be calculated for the individual stroke lengths. With these figures, the maximum resulting load F res, max can be calculated and then inserted in the equation for s 0. 28

29 V F res, max = MAXs F res, j s j=1 1 e q s M x s s M y s s M z s w r F res, max = MAX d F Pr +sf y s +sf z s +s JJJLLL + JJJLLL + JJJLLL sf x < s B s s 1 L T s s L T s z c Elaborated equation for the static safety factor All given equations related to the static safety factor can be integated into one formula: C 0, eff slide F res, max z T 2 f h0 f t C 0,10 JJ 10 f1 s 0 = JJJLLL = JJJJJJJJJJJJJJJJJJJJJJJJJLLLLLL V e q s M x s s M y s s M z s wr MAX d F Pr +sf y s +sf z s +s JJJLLL + JJJLLL + JJJLLL sf j=1 x < s B s s 1 L T s s L T s zc Elaborated equation for the rating life All given equations related to the rating life calculation can be integated into one formula: e q z T 2 w w q C w s f h f t C 10 JJL s eff slide < 10 f L ns = c 1 100s JJJs = c s JJJJJJK 1 z s < P z s 7 V p s s 7 Os Pj s Sj pp j=1 s JJJJL x S tot c r p e q z T 2 w w s f h f t C 10 JJL < s 10 f 1 z L ns = c s JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJK s V s 7 p t O fs,j s M x,j s s M y,j s s M z,j s yp s 7 s F Pr +sf y,j s +sf z,j s + JJJLLLL + JJJLLLL + JJJLLLL s S j s pp j=1 v s B 1 s s L T s s L T s b s JJJJJJJJJJJJJJJJJJJJJJJJJJJJJL x c S tot r p q q z T 2 w w w p f h f t C 10 JJL S < tot < 10 f 1 z z L ns = c JJJJJJJJJJJJJJJJJJJJJJJJJJJJJ V p t s M x,j s s M y,j s s M z,j s y p O f s,j s F Pr +sf y,j s +sf z,j s + JJJLLLL + JJJLLLL + JJJLLLL s S j j=1 v s B 1 s s L T s s L T s b 29

30 1.10 Example dimensioning calculation The customised SKF precision rail guide slide we will use for this example is equipped with an ironless linear motor with high velocity constancy as drive, with a sealed optical encoder and with mechanical end stops. The shown design is typical for precision rail guide slides ( fig. 17). Description of the application A construction part (mass 40 kg, length 150 mm, width 100 mm, height 90 mm) has to be moved in several process steps to perform a measurement. The first step is a very precise movement over its entire length. The measurement can be performed at a maximum acceleration of 1 m/s 2 and is running at constant room temperature of 22 C. The next process step, which is done at standstill, creates a load of 600 N downward in z-direction located symmetrically between the precision rail guide units and in x-direction 20 mm inside the construction part. The available construction space limits L rail by 250 mm. To have a certain reserve, the intended stroke of the slide is 160 mm. For forward and backward stroke the values for acceleration and deceleration are equal. Because of the high demands on repeatability of running accuracy in height- and sideward direction, an anti-creeping system is required. So the precision rail guides with ACSM have to be used. Questions to be answered: Which precision rail guide (size, L cage ) is sufficient for this application? Which maximum stroke will be possible? Which static safety factor and rating life in kilometers can be achieved? Maximum length of rolling element assembly In this example the geometry is given by the construction space and the demanded stroke. According to chapter 1.8.5, following formula has to be used: L cage, max = L rail 0,5 S L cage, max = 250 mm 0,5 160 mm = 170 mm Number of rolling elements z, z T Because of the chosen kinematic not overrunning cage without wipers, all rolling elements carry load all the time and z = z T. To calculate a real value of z, a certain type and size of rolling element assembly has to be chosen. Because of the fact that mass and external load are not too heavy in this example we start the calculation with the smallest possible cage type LWJK 2 ACSM which may fulfill the requirements. When checking the maximum rail length of LWRB2 we find out that 200 mm don t cover the needs and LWRE 3 ACSM is the smallest guiding possible. Following formula has to be used, as described in chapter The needed values are given in the relevant product chapter. q L cage, max t 1 t 2 t 3 w z = z T = TRUNC +1 < t z q 170 mm 2,65 mm 3,6 mm 9 mm w z = z T = TRUNC +1 = 25 < 6,25 mm z The number of rolling elements is used to calculate L cage needed for ordering: L cage = (z 1) t + t 1 + t 2 +t 3 L cage = (25 1) 6,25 mm + 2,65 mm + 3,6 mm + 9 mm = 165,25 mm The number of rolling elements is used to calculate the load carrying length L T : L T = (z T 1) t + t 3 L T = (25 1) 6,25 mm + 9 mm = 159 mm With the exact length of the cage, the resulting maximum stroke can be calculated. S = (L rail L cage ) 2 S = (250 mm 165,25 mm) 2 = 169,5 mm The general rules L cage = S for clamped arrangement and L T > B 1 are observed. Description Value Reasons for decision Table 6 f h0 factor for hardness, static 1 Compare chapter Influence of hardness, f h factor for hardness, dynamic 1 Compare chapter Influence of hardness, f t factor for operating temperature 1 Operating temperature far below 120 C f 1 factor for load direction 2 Clamped arrangement w rolling element exponent 7/9 Cage with rollers C 0,10 basic static load rating for 10 rollers 8160 N LWAKE 3 ACSM C 10 basic dynamic load rating for 10 rollers 5040 N LWAKE 3 ACSM 30

31 RLM with coordinate system Fig F z +z +F x +F y +x +y 30 M y F x, drive 5, M z M x Determination of effective load ratings For the calculation of the static safety factor and the rating life, the effective load ratings are needed. It is important to know several determining factors as shown in table 6. Furthermore the values of C 0,10 and C 10 of the selected rolling element assembly have to be gathered in the product chapter. z T 2 C 0, eff slide = f h0 f t C 0,10 10 f C 0, eff slide = N = N 10 2 q z T 2 w w C eff slide = f h f t C 10 < 10 f 1 z q 25 2 w 9 C eff slide = N = N < 10 2 z 7 31

32 Calculation of bearing loads Beside the effective load ratings it is also necessary to calculate the maximum resulting load F res, max and the equivalent dynamic mean load P m of the application. For that, it is essential to understand the workflow of the application and where and at what time the loads are acting. In most cases it is necessary to separate the workflow into load phases with constant or nearly constant conditions. The definition of the general coordinate system is shown in fig. 17 at the beginning of this chapter. Fig. 18 shows the lever arms in x-direction of load phase 6 of the example. For an explanation, where to set the coordinate system, see also chapter For each load phase the working loads have to be summarized to a set of five values: F y, F z, M x, M y, M z. After that, those five values and the preload force are transferred to one load which represents the respective load phase. The workflow of the application with its single load phases and the acting loads including their lever arms of the example are shown in following systematic overview ( table Load calculation, page 34 and 35). Also the needed formulas and calculations can be found there. Since the values for acceleration and deceleration are equal on forward and backward stroke, it is here sufficient to calculate P m only with the load phases of the forward stroke. The factor for stroke length has to be determined with the help of diagram 6, chapter ,5 (92,5) 55,0 F Fig. 18 S 150 mm = = 0,91 f s = 1 L cage 165,25 mm The preload force has to be calculated. The factor for preload f Pr depends on the type of rolling element assembly ( chapter ). F Pr = f Pr C eff slide F Pr = 0, N = 719,5 N 32

33 Maximum resulting load The maximum resulting load occurs in load phase 6. 1 V F res, max = MAX s F res, j s j=1 F res, max = N Calculation of the static safety factor Now for the chosen precision rail guide and the load phase with the highest resulting load, the static safety factor s 0 can be calculated. C 0, eff slide s 0 = F res, max N s 0 = = 4, N Equivalent dynamic mean load For the calculation of the rating life the equivalent dynamic mean load is needed. The single values, the needed formula and the calculations are given in table Load calculations, page 34 and 35. The result is 7 V p 7 Os Pj s Sj j=1 P m = p JJJJLL = N S tot Rating life calculation The rating life of precision rail guides expressed in km, L ns, can now be calculated using following formula: q C eff slide w p L ns = c km < P m z q N w 3 L 10s = km = km < N z 10 33

34 Load calculations Workflow divided in load phases Individual stroke length Sj: Accelleration: Speed: Position at beginning of load phase: Load phase 1 Acceleration, starting from left position 5 mm 1 m/s 2 Increasing 75 mm Comment: Forces in Newton [N] Lever arms in Meter [m] Torque loads in Newtonmeter [Nm] Lever arms x y z Name of force in x-direction Force Fx Driving force 40 0,035 0,0053 Inertia force ,075 Name of force in z-direction Force Fz Construction part 392,4 0, Additional load U F y = O F y,i i = 1 U F z = O F z,i i = 1 U M x = O F y,i z i +O F z,i y i i = 1 i = 1 U 0 392,4 0 U M y = O F x,i z i O F z,i x i i = 1 i = 1 U 17,93 U M z = O F x,i y i +O F y,i x i i = 1 i = 1 U q s M x s s M y s s M z s w F res = F Pr +sf y s +sf z s + s JJJLLL + JJJLLL + JJJLLL s < s B 1 s s L T s s L T s z t s M x s s M y s s M z s y P = f s F res = f s s F Pr +s Fys +s Fzs + JJJLLL + JJJLLL + JJJLLL s v s B 1 s s L T s s L T s b 1, , ,3 7 V p Os Pj s Sj 7 j=1 S tot P m = p JJJJL 34

35 Load phase 2 Constant speed Load phase 3 Constant speed Load phase 4 Constant speed Load phase 5 Deceleration Load phase 6 Right position at standstill with load 1 40 mm 0 m/s 2 0,1 m/s 70 mm 60 mm 0 m/s 2 0,1 m/s 0 mm 40 mm 0 m/s 2 0,1 m/s 70 mm 5 mm 1 m/s 2 Decreasing 70 mm 0 mm 0 m/s 2 0 m/s 75 mm Lever arm is decreasing. As assumption the worst case is chosen for the whole load phase. Lever arm is decreasing, becomes zero and is increasing. As assumption the lever arm is set to zero for the whole load phase. Lever arm is increasing. As assumption the lever arm from the end of this load phase is chosen (worst case). Lever arms Lever arms Lever arms Lever arms Lever arms x x x x y z x y z Force Fx Force Fx Force Fx Force Fx Force Fx 40 0,035 0, ,075 Force Fz Force Fz Force Fz Force Fz Force Fz 392,4 0, , ,4 0, ,4 0, ,4 0, , ,4 392,4 392,4 392,4 992, , ,73 16,95 70, , , , , , , , , , , , ,3 N 10/3 5 mm N 10/3 40 mm ,9 N 10/3 60 mm N 10/3 40 mm ,4 N 10/3 5 mm P m = 7 10/3 = N P 5 mm + 40 mm + 60 mm + 40 mm + 5 mm 35

36 1.11 Rigidity calculation For the user of precision rail guide systems it is of particular importance to be able to calculate the elastic deflection of the arrangement at the point where the load is applied. To get an approximation of this figure, it is at first necessary to determine the elastic deformation caused by the rolling element on the raceway d, by using one of the diagrams This value has to be multiplied with factor f k, to achieve an approximate value for the resulting deflection d res, that a precision rail guide system, including the adjacent parts made of steel, will have. Following two chapters describe this procedure Determination of elastic deformation using the nomogram When using a nomogram from diagram 8 11 it is first necessary to establish the load conditions in relation to the mechanical dimensions and to define for which load phase and dominating single load in z-direction the elastic deformation should be calculated. Figure 19 shows the necessary parameters required for the calculation. The rolling element diameter D w and the contact length of rolling element L w eff can be obtained from table 7. After these calculations the elastic deformation for the point where the load is applied can be read off the nomogram. The nomograms are based on clamped rail guides ( chapter 1.8.4) and relate as follows to the various types of precision rail guides. There is a calculation example in chapter , for which diagram 8 and 10 already contain the values and lines. Leverage ratio 1 Contact length Rolling element assembly t L T Diameter of rolling element D w x F z Contact length of rolling element L w eff mm mm F z B 1 y Product series LWJK 1,588 1,588 r LWJK 2 2 s LWAK 3 3 1,1 f LWR LWAL 6 6 2,4 s LWAL 9 9 3,6 s LWAL ,4 c LWAKE 3 4 2,3 r LWAKE 4 6,5 3,2 s LWAKE 6 8 4,7 f LWRE LWAKE ,2 c LWHV ,4 r s s LWHW ,4 LWHV ,4 LWHW ,4 LWHV 20 2,5 11,4 LWHW 20 2,5 9,4 LWHW ,4 LWHW 30 3,5 17,4 f LWRM/V LWM/V s s c Fig. 19 Table 7 Diagram 8: LWR rail guides with crossed roller assembly Diagram 9: LWR rail guides with ball assembly Diagram 10: LWRE rail guides with crossed roller assembly Diagram 11: LWRM/LWRV and LWM/LWV rail guides with needle roller assembly 36

37 Preparation Determination of number of load carrying rolling elements ( chapter and 1.8.6): L T z T = + 1 t Identify the elastic deformation in the nomogram The values created in section preparation are now needed to finally identify the elastic deformation d in the nomogram ( diagram 8 11). 1 Calculation of average rolling element load for: Ball and crossed roller assembly: F z Q = zt Needle roller assembly: F z Q = 2 z t Calculation of the leverage ratio R x : x R x = t Calculation of the leverage ratio R y : y R y = B 1 Where z T = number of load carrying rolling elements (per cage or per row for needles) L T = load carrying length [mm] t = pitch of rolling elements in cage [mm] Q = average load per rolling element [N] F z = single load in z-direction [N] x = distance from centre of rolling element assembly to point of application of load [mm] y = distance from centre of rail guide unit to point of application of load [mm] B 1 = mean distance between the rolling element assemblies [mm] D w = rolling element diameter [mm] L w eff = contact length of rolling element [mm] 37

38 10 Diagram 8 Nomogram of elastic deformation for LWR rail guides with crossed roller assembly R x = x t R y = y B ,2 1,0 0,8 0 0,2 0,4 0, z T d µm Q D w

39 Nomogram of elastic deformation for LWR rail guides with ball assembly Diagram 9 1 R x = x t R y= y B ,2 1,0 0,8 0,6 0,4 0 0, z T d µm Q ,5 D w 10 39

40 40 Diagram 10 Nomogram of elastic deformation for LWRE rail guides with high capacity crossed roller assembly R x = x t R y = y B ,2 1,0 0,8 0,60 0, z T d µm L w eff 5 Q 40

41 Nomogram of elastic deformation for LWRM / LWRV and LWM / LWV rail guides with needle roller assembly Diagram 11 1 R x = x t R y = y B ,2 1,0 0,8 0,6 0,4 0, z T d µm Q 14 8 L w eff 41

42 Determination of resulting deflection of a rail guide system When comparing the measured elastic deflection of a complete slide system with the values of the nomograms, the rigidity of the complete slide system will be found to be significantly less. This discrepancy is mainly due to uneven load distribution along the guide. This happens because inaccuracies of form, deviation from parallelism, improper mounting, etc. and can lead to variations in the loading of the single rolling element along the rail guide. By using factor f k, which is based on the number of load carrying rolling elements z T and the specific load on a rolling element k, attention is paid to this circumstances. The relevant values of f k for LWRE rail guides with crossed roller assembly and LWRM/LWRV rail guides or LWM/LWV rail guides with needle roller assembly can be obtained from diagram 12. When calculating the elastic deflection of an LWR rail guide, the correction factor f k has to be obtained from diagram 13. When using LWR rail guides with ball assembly the calculated values conform to the measurements and no factor f k is needed. For the calculation example in chapter , both diagrams already contain the values and lines. Determination of the specific load per rolling element: for LWR crossed roller assembly: where k = specific load per rolling element [N/mm 2 ] F z = single load in z-direction [N] z T = number of load carrying rolling elements (per cage or per row for needles) D w = rolling element diameter [mm] L w eff = contact length of rolling element [mm] Correction factor f k for LWRE, LWRM/LWRV or LWM/LWV rail guides f k 6,0 5,0 4,0 3,0 2,0 1,5 k = 1 Diagram 12 1, LWRE crossed roller assembly Needle roller assembly Number of load carrying rolling elements z T F z k = z T D w 2 for LWRE crossed roller assembly: Correction factor f k for LWR rail guides Diagram 13 F z k = z T D w L w eff for needle roller assembly: f k 2,4 2,3 2,2 2,0 2 1,9 1,8 k = F z k = 2 z T D w L w eff 1,6 1,4 1, , Number of load carrying rolling elements z T 42

43 Calculation of resulting deflection: d res = f k d where d res = resulting deflection [µm] d = elastic deformation (determined in nomogram) [µm] = correction factor f k Calculation example for the resulting deflection The standard SKF GCL 6400 slide is loaded in an extended position with a load of N as shown in table 8. What is the resulting deflection of the LWR6 rail guide at the point where the load is applied in this case? How great would this have been for a LWRE6 rail guide? Following values have to be determined ( table 8). Calculation example for the resulting deflection L T max = 260 x = 240 F z = N Parameter Unit LWR LWRE Load carrying length L T mm Pitch of rolling element assembly t mm 9 11 Number of load carrying rolling elements z T Leverage ratio R x = x/t 26,7 21,8 Leverage ratio R y = y/b 1 0,44 0,44 Rolling element diameter D w mm 6 8 Contact length of rolling element L w eff mm 2,4 4,7 Average load per rolling element Q N 34,5 41,7 Elastic deformation d (determined in nomogram) µm 22,5 13 Specific load per rolling element k N/mm 2 0,96 1,1 Correction factor f k 1,99 2,9 Resulting deflection d res µm F z B 1 = 45 y = 20 Table

44 1.12 Technical data of precision rail guides with slide coating Surface pressure To achieve a reasonable value for the contact deformation, the surface pressure of plain bearings or guidings is normally in the region of 0,2 to 1 N/mm 2. Diagram 14 shows the surface deformation of Turcite-B rail guides expressed in relation to surface pressure. In case of overload, up to 6 N/mm 2, the contact deformation rises to 5 µm but recovers to the original dimension when the load is relieved Wear LWRPM / LWRPV rail guides are characterised by their high resistance to wear. The ground surface of the LWRPV guides is matched to suit the Turcite-B so that the degree of wear is kept to a minimum. Even a certain amount of contamination can be tolerated without affecting the sliding qualities since the slide material is capable of allowing small particles to become embedded in the surface. For optimum performance, however, lubrication of the LWRPM / LWRPV rail guides is recommended. As seen in diagram 15, the oil-lubricated guide (curve 1) shows less wear along the length of travel in comparison with the non-lubricated guide (curve 2). The values indicated are for an average surface pressure of 0,4 N/mm Frictional properties Due to the favourable frictional qualities of Turcite-B, the running speed of a dry sliding rail guide has relatively little effect on the coefficient of friction, and stickslip is virtually eliminated. Diagram 16 illustrates the relationship between the coefficient of friction for LWRPM / LWRPV rail guides as a function of sliding speed. Curve 1 applies to an oillubricated guide, and curve 2 applies to a non-lubricated installation. The degree of friction is seen to fall during a smoothing phase and then remains relatively constant. The values indicated are based on an average surface pressure of 0,2 N/mm 2. Diagram 14 Contact deformation in relation to suface pressure Contact deformation, [µm] 4 3,5 3 2,5 2 1,5 1 0, ,25 0,50 0,75 1,00 1,25 1,50 1,75 2,00 Surface pressure [N/mm 2 ] Diagram 15 Wear in relation to length of travel Wear [µm] (dry) 10 1 (lubricated) Travel [km] Diagram 16 Coefficient of friction as a function of sliding speed Coefficient of friction 0,28 0,24 0,20 0,16 2 (dry) 0,12 0,08 0,04 1 (lubricated) Speed [mm/min] 44

45 Diagram 17 shows the coefficient of friction for an oil-lubricated LWRPM / LWRPV rail guide in relation to the surface pressure. Here it will be seen that the coefficient of friction for low load conditions is relatively high, but when the surface pressure reaches 0,2 N/mm 2, the coefficient falls to a minimum and remains constant. Coefficient of friction as a function of surface pressure Coefficient of friction 0,10 0,08 Diagram Temperature range The operating temperature of a linear plain bearing should lie between the limits of 40 C and +80 C. Higher temperatures tend to reduce the pressure resistance. In many cases, the dissipation of heat can be enhanced through the use of lubricating oil. 0,06 0,04 0, ,1 0,2 (lubricated) 0,3 0,4 Surface pressure [N/mm 2 ] Chemical and humidity resistance Turcite-B possesses excellent chemical resistance. Moisture absorbency amounts to a maximum of 0,01 percent and has no significant dimensional effect. Sliding surfaces of Turcite-B are consequently highly resistant to cool conditions and the effect of lubricating oils. 45

46 1.13 Legend Table 9 Legend B 1 mean distance between the rolling element assemblies [mm] C dynamic load rating [N] C 0 static load rating [N] C 10 basic dynamic load rating of a cage with 10 rolling elements (balls, rollers) or with 2 rows of 10 needles under load [N] C 0,10 basic static load rating of a cage with 10 rolling elements (balls, rollers) or with 2 rows of 10 needles under load [N] C eff effective dynamic load rating of one cage [N] C eff slide effective dynamic load rating of a slide [N] C 0, eff slide effective static load rating of a slide [N] c 1 factor for reliability d elastic deformation (determined in nomogram) [µm] d res resulting deflection [µm] EG length of lead in radius on each side [mm] f 1 factor for load direction f h factor for hardness, dynamic f h0 factor for hardness, static f k correction factor f Pr factor for preload [%] f s, f s,j factor for stroke length f t factor for operating temperature F Pr preload force [N] F res resulting load [N] F res max maximum resulting load [N] F x,i, F y,i, F z,i single loads in x-, y- or z-direction that act simultaneously on the rail guide system [N] F y, F z summarized force (load) in y- or z-direction [N] k specific load per rolling element [N/mm 2 ] L 10h basic rating life [h] L 10s basic rating life [km] L ns modified basic rating life [km] L cage length of rolling element assembly [mm] L cage, max maximum length of rolling element assembly, if length of rail and stroke are predefined [mm] L install length of the complete installation [mm] L rail length of the rail [mm] L rail, min minimum length of the rail, if length of cage and stroke are predefined [mm] L rail, long length of the long rail [mm] L rail, long, min minimum length of the long rail, if length of cage and stroke are predefined [mm] L rail, short length of the short rail in an overrunning system [mm] L T load carrying length [mm] L w eff contact length of rolling element [mm] M x, M y, M z summarized torque loads in x-, y- or z-direction [Nm] n stroke frequency [double strokes/min] p life exponent; p = 3 for balls, p = 10/3 for rollers P equivalent dynamic load [N] P m equivalent dynamic mean load [N] P 0 maximum static load [N] Q average load per rolling element [N] R x leverage ratio in x-direction leverage ratio in y-direction R y s 0 static safety factor S intended stroke length [mm] S j individual stroke length [mm] S tot total stroke length [mm] x i, y i, z i, lever arms that are related to the single loads [m] w z z T rolling element exponent; w = 0,7 for balls, w = 7/9 for rollers number of rolling elements (per cage or per row for needles) number of load carrying rolling elements (per cage or per row for needles) Dimensions from product data: A Width of precision rail guide [mm] L thickness of end piece [mm] L 1 thickness of end piece with wiper [mm] t pitch of rolling elements in cage [mm] t 1, t 2 distance of outer rolling element to the end of the cage [mm] t 3 length of anti-creeping system [mm] J 1 length between end of rail and first mounting hole [mm] Indizes i U j V counter for single loads in x-, y- or z-direction that act simultaneously amount of loads that act simultaneously counter for load phases amount of load phases 46

47 2 Product data LWR / LWRB Rail guides LWR and LWRB rail guides are well-proven, limited-travel linear guides used in numerous applications. They can be used with crossed roller assemblies or ball assemblies, depending on the respective application. LWR rail guides with crossed roller assemblies are preferred for high load carrying capacity and good rigidity behaviour. LWRB rail guides with ball assembly can be used where loads are light and/or easy running is required. The small cross-section is ideal for applications with limited space. Rolling element assemblies LWJK ball assemblies, which are used together with LWRB rails, are provided with a ball-retaining plastic cage. These are available for sizes 1 and 2. LWAK crossed roller assemblies comprise a plastic cage with retained cylindrical rollers, available as standard for size 3. LWAL crossed roller assemblies, consisting of an aluminium cage with retained rollers, are available in sizes 6 to 12. End pieces End pieces prevent drift of the cage away from the loaded zone. Available types are LWERA, LWERB as standard end pieces, and LWERC as end pieces with wipers. All end pieces are supplied with appropriate mounting screws. Ordering example: 4x LWR x LWAL 9x25 8x LWERA 9 47

48 LWR precision rail guides J 3 D w A 1 G 1 J 3 D w A 1 G 1 B N 1 B N 1 A J 2 G N A J 2 G N LWR LWRB G 3 G 2 J 1 J J 1 L Designation 1) Dimensions Weight Mounting holes End face holes A B A 1 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 G 2 G 3 mm kg/m mm mm mm mm LWRB 1 8,5 4 3,9 1,588 0, ,8 M2 1,65 3 1,4 1,9 M1,6 2 LWRB ,5 2 0, ,5 7,5 2,5 M3 2,55 4,4 2 2,7 M2,5 3 Designation 1) Dimensions Weight Mounting holes End face holes A B A 1 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 G 2 G 3 mm kg/m mm mm mm mm LWR ,2 3 0, ,5 12,5 3,5 M4 3,3 6 3,2 4 M3 6 LWR ,9 6 1, M6 5,2 9,5 5,2 7 M5 9 LWR ,7 9 3, M8 6,8 10,5 6,2 10 M6 9 LWR ,9 12 5, M10 8,5 13,5 8,2 13 M8 12 1) Sizes LWR 15, 18 and 24 are available on request. 48

49 LWR rail guides in kit packaging Designation Load ratings 1) Stroke 2) Type of rail Type of cage Type of end piece dyn. stat. standard max 4 pieces 2 pieces 8 pieces C C 0 N mm 2 LWR 3050 Kit LWR 3050 LWAK 3x7 LWERA 3 LWR 3075 Kit LWR 3075 LWAK 3x11 LWERA 3 LWR 3100 Kit LWR 3100 LWAK 3x15 LWERA 3 LWR 3125 Kit LWR 3125 LWAK 3x18 LWERA 3 LWR 3150 Kit LWR 3150 LWAK 3x22 LWERA 3 LWR 3175 Kit LWR 3175 LWAK 3x26 LWERA 3 LWR 3200 Kit LWR 3200 LWAK 3x30 LWERA 3 LWR Kit LWR 6100 LWAL 6x8 LWERA 6 LWR Kit LWR 6150 LWAL 6x12 LWERA 6 LWR Kit LWR 6200 LWAL 6x16 LWERA 6 LWR Kit LWR 6250 LWAL 6x20 LWERA 6 LWR 6300 Kit LWR 6300 LWAL 6x25 LWERA 6 LWR 6350 Kit LWR 6350 LWAL 6x29 LWERA 6 LWR 6400 Kit LWR 6400 LWAL 6x33 LWERA 6 1) Load ratings are given for a kit of 4 rails and 2 cages in clamped arrangement. 2) Cage length is adjustable but must not be shorter than 2/3 of the total rail length. Available lengths 1) Maximum rail length L mm mm l l l l l L L L L 150 l l l l l l l L L 200 Available lengths 1) L mm Maximum rail length mm l l l l l l l L l L l 400 l L l l l l l l l l L L L L l l l l L L L L L L L L L L L L L L L L L L ) Other rail lengths are available on request but new J 1 dimension has to be calculated as described in chapter 3.1.7, Calculation of J 1 dimension. l) Prompt delivery L) Delivery time on request 49

50 Ball and crossed roller assemblies t 1 t t 1 t t 1 t D w D w D w U U U U 1 U 1 U 1 LWJK LWAK LWAL Designation Dimensions Load ratings for 10 rolling elements dynamic static D w U U 1 t t 1 C 10 C 0 10 Maximum cage length Appropriate rail guide mm N Balls/Rollers LWJK 1,588 1,588 3,5 0,5 2, LWRB 1 LWJK ,75 3,9 1, LWRB 2 LWAK 3 3 7, , LWR 3 LWAL ,8 2, LWR 6 LWAL , LWR 9 LWAL LWR 12 50

51 LWR end pieces L L L 2 LWERA 1+2 LWERA 3 12 LWERB 1+2 LWERB 1 LWERB 2 L L 1 wiper LWERB 3 12 LWERC 3 12 Designation Dimensions Attachment screw Appropriate rail End pieces End pieces ISO 1580 ISO guide with wiper L L 1 mm LWERA 1 1 LWRB 1 LWERB 1 1,8 M 1,6 LWERA 2 1,5 LWRB 2 LWERB 2 2 M 2,5 LWERA 3 2,5 LWR 3 LWERB 3 2 M 3 LWERC 3 5 M 3 LWERA 6 3 LWR 6 LWERB 6 3 M 5 LWERC 6 6 M 5 LWERA 9 4 LWR 9 LWERB 9 4 M 6 LWERC 9 7 M 6 LWERA 12 5 LWR 12 LWERB 12 5 M 8 LWERC 12 8 M 8 51

52 2.2 LWRE Rail guides LWRE rail guides are a logical development of the proven LWR rail guides. In addition to the familiar characteristics of the LWR series, the LWRE rail guides offer the advantages of fivefold load ratings and a doubling of the rigidity. This means that for the same load capacity, a 50% reduction in bearing size compared with the standard LWR rail guide is possible ( fig. 1). Alternatively, with the same outer dimensions, greatly increased static safety and lifetime results. The improvements are achieved through optimized internal geometry in conjunction with larger roller diameters. Furthermore, LWRE rail guides utilise the whole roller length so that no tilting moment or edge stresses can occur ( fig. 2). The mounting and attachment dimensions of the LWRE rail guides conform to those of all the SKF Modular Range rail guides included in this catalogue. Rolling element assemblies LWAKE crossed roller cages consist of individual plastic elements. In LWAKE 3, 6 and 9 cages, these elements are assembled using a snap in technique, whereby each element can be rotated manually through an angle of 90 ( fig. 3). The load rating and rigidity can be increased by turning the rollers in the direction of the main load. As standard, the orientation of the rollers is alternating. The cage retains the rollers and at the same time almost fills the free space between the rails, thus providing good protection against ingress of dirt. LWAKE 4 cages consist of roller segments fitted together to the customer s specific length requirements. Individual rotating is not possible for size 4. End pieces End pieces prevent drift of the cage away from the loaded zone. LWERE end pieces are generally used for horizontal and vertical applications. An end piece with wiper, LWEREC, is available. All end pieces are supplied with appropriate mounting screws. Ordering example: 4x LWRE x LWAKE 6x13 8x LWERE 6 52

53 Fig. 1 Fig. 2 L w eff = 2,4 LWR 12 P = N mm2 Q LWR 6 M LWRE 6 L w eff = 4,7 Dw = 6 Q M = Q x e P = N mm2 Q e = 1,2 LWRE 6 M M = 0 Dw = 8 Q e = 0 Fig. 3 53

54 LWRE precision rail guides J 3 D w G 1 A 1 B N 1 A J 2 G N G 3 G 2 J 1 J J 1 L Designation Dimensions Weight Mounting holes End face holes A B A 1 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 G 2 G 3 mm kg/m mm mm mm mm LWRE ,7 4 0, ,5 12,5 3,5 M 4 3,3 6 3,2 4 M 3 6 LWRE ,5 0, ,5 12,5 5 M 4 3,3 6 3,2 5 M 3 6 LWRE ,2 8 1, M 6 5,2 9,5 5,2 6,75 M 5 9 LWRE ,7 12 3, M 8 6,8 10,5 6,2 9,75 M 6 9 Designation Dimensions Weight Mounting holes End face holes A B A 1 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 G 2 G 3 mm kg/m mm mm mm mm LWRE ,7 4 0, ,5 M 5 4,3 7,5 4,1 6 M

55 LWRE rail guides in kit packaging Designation Load ratings 1) Stroke 2) Type of rail Type of cage Type of end piece dyn. stat. standard max 4 pieces 2 pieces 8 pieces C C 0 N mm 2 LWRE 3050 Kit LWRE 3050 LWAKE 3x6 LWERE 3 LWRE 3075 Kit LWRE 3075 LWAKE 3x9 LWERE 3 LWRE 3100 Kit LWRE 3100 LWAKE 3x12 LWERE 3 LWRE 3125 Kit LWRE 3125 LWAKE 3x15 LWERE 3 LWRE 3150 Kit LWRE 3150 LWAKE 3x18 LWERE 3 LWRE 3175 Kit LWRE 3175 LWAKE 3x21 LWERE 3 LWRE 3200 Kit LWRE 3200 LWAKE 3x24 LWERE 3 LWRE 4100 Kit LWRE 4100 LWAKE 4x10 LWERE 4 LWRE 4150 Kit LWRE 4150 LWAKE 4x15 LWERE 4 LWRE 4200 Kit LWRE 4200 LWAKE 4x19 LWERE 4 LWRE 4250 Kit LWRE 4250 LWAKE 4x24 LWERE 4 LWRE 4300 Kit LWRE 4300 LWAKE 4x28 LWERE 4 LWRE 4350 Kit LWRE 4350 LWAKE 4x33 LWERE 4 LWRE 4400 Kit LWRE 4400 LWAKE 4x38 LWERE 4 LWRE 6100 Kit LWRE 6100 LWAKE 6x7 LWERE 6 LWRE 6150 Kit LWRE 6150 LWAKE 6x10 LWERE 6 LWRE 6200 Kit LWRE 6200 LWAKE 6x14 LWERE 6 LWRE 6250 Kit LWRE 6250 LWAKE 6x17 LWERE 6 LWRE 6300 Kit LWRE 6300 LWAKE 6x20 LWERE 6 LWRE 6350 Kit LWRE 6350 LWAKE 6x24 LWERE 6 LWRE 6400 Kit LWRE 6400 LWAKE 6x27 LWERE 6 1) Load ratings are given for a kit of 4 rails and 2 cages in clamped arrangement. 2) Cage length is adjustable but must not be shorter than 2/3 of the total rail length. Available lengths 1) L mm Maximum rail length mm l l l l l l l L L L L 400 l l l l l l L L L L L 700 l l l l l L l L L L L L L l l l l l L L L L Available lengths 1) Maximum rail length L mm mm L L L L L L L L L 500 1) Other rail lengths are available on request but new J 1 dimension has to be calculated as described in chapter 3.1.7, Calculation of J 1 dimension. l) Prompt delivery L) Delivery time on request 55

56 Crossed roller assemblies D w t 1 t t 2 D w t 1 t t 2 LWAKE 3, 6, 9 LWAKE 4 Designation Dimensions Load ratings for 10 rolling elements dynamic static D w t t 1 t 2 C 10 C 0 10 Maximum cage length 1) Appropriate rail guide mm N mm LWAKE 3 4 6,25 2,65 3, LWRE 3, LWRE 2211 LWAKE 4 6,5 8 4,3 4, LWRE 4 LWAKE LWRE 6 LWAKE ,35 8, LWRE 9 1) Longer cages are available on request. LWRE end pieces L L 1 L wiper LWERE 3, 6, 9 LWEREC 3, 6, 9 LWERE 4 Designation Dimensions Attachment screw Appropriate rail End pieces End pieces ISO guide with wiper L L 1 mm LWERE 3 2 M 3 LWRE 3, LWRE 2211 LWEREC 3 4 M 3 LWRE 3, LWRE 2212 LWERE 4 4 M 3 (DIN 7984) LWRE 4 LWERE 6 3 M 5 LWRE 6 LWEREC 6 5 M 5 LWRE 6 LWERE 9 3 M 6 LWRE 9 LWEREC 9 6 M 6 LWRE 9 56

57 2.3 LWRE ACS Rail guides Rolling element assemblies End pieces LWRE ACS rail guides are identical to LWRE rail guides, but designed for use with anticreeping LWAKE ACS cages. The non-slip effect is achieved through a patented control gear attached to the cage, which is in mesh between the LWRE ACS rails during operation, thus retaining the cage in its defined position. As standard, the rails are prepared for maximum stroke ( chapter 1.4). In principle, LWAKE ACS are the same as LWAKE cages, whereby LWAKE ACS crossed roller cages incorporate an additional control gear located at the centre of the cage. The load carrying capacity of LWAKE ACS cages is also identical with that of LWAKE standard cages, assuming that they comprise an identical number of rollers. However, consider that due to their additional control gear, LWAKE ACS cages are longer than the corresponding LWAKE cages, even if the number of rollers is identical. Overrunning cages should only be used after consulting SKF. End pieces are generally not needed, but for production reasons, the tapped holes on the rail s end face are standard and end pieces can be mounted. LWERE end pieces are generally used for horizontal and vertical applications. An end piece with wiper, LWEREC, is available. All end pieces are supplied with appropriate mounting screws. The end pieces for LWRE rail guides are also suitable for LWRE ACS rail guides. Ordering example for rail with maximum stroke: 4x LWRE 6200 ACS 2x LWAKE 6x12 ACS 8x LWERE

58 LWRE ACS precision rail guides J 3 D w G 1 A 1 B N 1 A J 2 G N G 3 G 2 J 1 J J 1 L Designation Dimensions Weight Mounting holes End face holes A B A 1 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 G 2 G 3 mm kg/m mm mm mm mm LWRE 3 ACS ,7 4 0, ,5 12,5 3,5 M 4 3,3 6 3,2 4 M 3 6 LWRE 4 ACS ,5 0, ,5 12,5 5 M 4 3,3 6 3,2 5 M 3 6 LWRE 6 ACS ,2 8 1, M 6 5,2 9,5 5,2 6,75 M 5 9 LWRE 9 ACS ,7 12 3, M 8 6,8 10,5 6,2 9,75 M 6 9 Designation Dimensions Weight Mounting holes End face holes A B A 1 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 G 2 G 3 mm kg/m mm mm mm mm LWRE 2211 ACS ,7 4 0, ,5 M 5 4,3 7,5 4,1 6 M

59 LWRE ACS rail guides in kit packaging Designation Load ratings 1) Stroke 2) Type of rail Type of cage Type of end piece dyn. stat. standard max 4 pieces 2 pieces 8 pieces C C 0 N mm 2 LWRE 3050 ACS Kit LWRE 3050 ACS LWAKE 3 x 5 ACS LWERE 3 LWRE 3075 ACS Kit LWRE 3075 ACS LWAKE 3 x 6 ACS LWERE 3 LWRE 3100 ACS Kit LWRE 3100 ACS LWAKE 3 x 10 ACS LWERE 3 LWRE 3125 ACS Kit LWRE 3125 ACS LWAKE 3 x 13 ACS LWERE 3 LWRE 3150 ACS Kit LWRE 3150 ACS LWAKE 3 x 16 ACS LWERE 3 LWRE 3175 ACS Kit LWRE 3175 ACS LWAKE 3 x 18 ACS LWERE 3 LWRE 3200 ACS Kit LWRE 3200 ACS LWAKE 3 x 22 ACS LWERE 3 LWRE 4100 ACS Kit LWRE 4100 ACS LWAKE 4x8 ACS LWERE 4 LWRE 4150 ACS Kit LWRE 4150 ACS LWAKE 4x12 ACS LWERE 4 LWRE 4200 ACS Kit LWRE 4200 ACS LWAKE 4x17 ACS LWERE 4 LWRE 4250 ACS Kit LWRE 4250 ACS LWAKE 4x21 ACS LWERE 4 LWRE 4300 ACS Kit LWRE 4300 ACS LWAKE 4x26 ACS LWERE 4 LWRE 4350 ACS Kit LWRE 4350 ACS LWAKE 4x31 ACS LWERE 4 LWRE 4400 ACS Kit LWRE 4400 ACS LWAKE 4x35 ACS LWERE 4 LWRE 6100 ACS Kit LWRE 6100 ACS LWAKE 6 x 6 ACS LWERE 6 LWRE 6150 ACS Kit LWRE 6150 ACS LWAKE 6 x 9 ACS LWERE 6 LWRE 6200 ACS Kit LWRE 6200 ACS LWAKE 6 x 12 ACS LWERE 6 LWRE 6250 ACS Kit LWRE 6250 ACS LWAKE 6 x 16 ACS LWERE 6 LWRE 6300 ACS Kit LWRE 6300 ACS LWAKE 6 x 19 ACS LWERE 6 LWRE 6350 ACS Kit LWRE 6350 ACS LWAKE 6 x 23 ACS LWERE 6 LWRE 6400 ACS Kit LWRE 6400 ACS LWAKE 6 x 26 ACS LWERE 6 1) Load ratings are given for a kit of 4 rails and 2 cages in clamped arrangement. 2) Cage length is adjustable but must not be shorter than 2/3 of the total rail length. Available lengths 1) L mm Maximum rail length mm l l l l l l l L L L L 400 L L L L L L L L L L L 700 l l l L l L l L l L L L L L L L L L L L L L Available lengths 1) Maximum rail length L mm mm L L L L L L L L L 500 1) Other rail lengths are available on request but new J 1 dimension has to be calculated as described in chapter 3.1.7, Calculation of J 1 dimension. l) Prompt delivery L) Delivery time on request 59

60 Crossed roller assemblies D w t 1 t t 2 t 3 D w t 1 t t 3 t 2 LWAKE 3, 6, 9 ACS LWAKE 4 ACS Designation Dimensions Load ratings for 10 rolling elements dynamic static D w t t 1 t 2 t 3 C 10 C 0 10 Maximum cage length 1) Appropriate rail guide mm N mm LWAKE 3 ACS 4 6,25 2,65 3, LWRE 3 ACS, LWRE 2211 ACS LWAKE 4 ACS 6,5 8 4,3 4, LWRE 4 ACS LWAKE 6 ACS LWRE 6 ACS LWAKE 9 ACS ,35 8,65 21, LWRE 9 ACS 1) Longer cages are available on request. LWRE ACS end pieces L L 1 L wiper LWERE 3, 6, 9 LWEREC 3, 6, 9 LWERE 4 Designation Dimensions Attachment screw Appropriate rail End pieces End pieces ISO guide with wiper L L 1 mm LWERE 3 2 M 3 LWRE 3, LWRE 2211 LWEREC 3 4 M 3 LWRE 3, LWRE 2212 LWERE 4 4 M 3 (DIN 7984) LWRE 4 LWERE 6 3 M 5 LWRE 6 LWEREC 6 5 M 5 LWRE 6 LWERE 9 3 M 6 LWRE 9 LWEREC 9 6 M 6 LWRE 9 60

61 2.4 LWRE / LWRB ACSM Rail guides Rolling element assemblies End pieces The refinement of our own ACS solution became the LWRE and LWRB ACSM rail guide version. LWRE and LWRB ACSM rail guides have the same outer dimensions as those without ACSM, but are designed for use with anti-creeping LWAKE ACSM cages. This cage, with an involute-toothed control gear made of brass and involute teeth directly machined into the rail, prevent cage-creeping very effectively and are especially suited for applications with high accelerations ( chapter 1.4). These rails are made of stainless steel as standard. In principle, LWAKE ACSM cages are the same as LWAKE cages, whereby LWAKE ACSM crossed roller cages incorporate an additional control gear made of brass located at the centre of the cage. When defining the cage length, the additional length of the control gear should be considered. Overrunning cages should only be used after consulting SKF. The given load capacities are already calculated for stainless steel rails, which means factor f h remains at one for calculation of the lifetime. Generally, the LWRE ACSM rail guides are not designed for use with end pieces. However, if required, this must be stated separately in the ordering code of the rail (Option E7). The end pieces for LWRE rail guides are also suitable for LWRE ACSM rail guides. Ordering example: 4x LWRE 3150 ACSM 2x LWAKE 3x16 ACSM 2 61

62 LWRE ACSM precision rail guides J 3 D w G 1 A 1 B N 1 A J 2 G N G 3 G 2 J 1 J J 1 L Designation Dimensions Weight Mounting holes End face holes 1) A B A 1 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 G 2 G 3 mm kg/m mm mm mm mm LWRB 2 ACSM ,5 2 0, ,5 7,5 2,5 M3 2,55 4,4 2 2,7 M2,5 3 LWRE 3 ACSM ,7 4 0, ,5 12,5 3,5 M 4 3,3 6 3,2 4 M 3 6 LWRE 4 ACSM ,5 0, ,5 12,5 5 M 4 3,3 6 3,2 5 M 3 6 LWRE 6 ACSM ,2 8 1, M 6 5,2 9,5 5,2 6,75 M 5 9 LWRE 9 ACSM ,7 12 3, M 8 6,8 10,5 6,2 9,75 M 6 9 Designation Dimensions Weight Mounting holes End face holes 1) A B A 1 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 G 2 G 3 mm kg/m mm mm mm mm LWRE 2211 ACSM ,7 4 0, ,5 M 5 4,3 7,5 4,1 6 M 3 6 1) Standard is without end face holes; Option E7 means with end face holes (blue lines) 62

63 LWRE ACSM rail guides in kit packaging Designation Load ratings 1), 2) Stroke 3) Type of rail Type of cage dyn. stat. standard max 4 pieces 2 pieces C C 0 N mm 2 LWRE 3050 ACSM Kit LWRE 3050 ACSM LWAKE 3 x 5 ACSM LWRE 3075 ACSM Kit LWRE 3075 ACSM LWAKE 3 x 6 ACSM LWRE 3100 ACSM Kit LWRE 3100 ACSM LWAKE 3 x 10 ACSM LWRE 3125 ACSM Kit LWRE 3125 ACSM LWAKE 3 x 13 ACSM LWRE 3150 ACSM Kit LWRE 3150 ACSM LWAKE 3 x 16 ACSM LWRE 3175 ACSM Kit LWRE 3175 ACSM LWAKE 3 x 18 ACSM LWRE 3200 ACSM Kit LWRE 3200 ACSM LWAKE 3 x 22 ACSM LWRE 6100 ACSM Kit LWRE 6100 ACSM LWAKE 6 x 6 ACSM LWRE 6150 ACSM Kit LWRE 6150 ACSM LWAKE 6 x 9 ACSM LWRE 6200 ACSM Kit LWRE 6200 ACSM LWAKE 6 x 12 ACSM LWRE 6250 ACSM Kit LWRE 6250 ACSM LWAKE 6 x 16 ACSM LWRE 6300 ACSM Kit LWRE 6300 ACSM LWAKE 6 x 19 ACSM LWRE 6350 ACSM Kit LWRE 6350 ACSM LWAKE 6 x 23 ACSM LWRE 6400 ACSM Kit LWRE 6400 ACSM LWAKE 6 x 26 ACSM 1) Load ratings are given for a kit of 4 rails and 2 cages in clamped arrangement. 2) Calculated with HRC 55 due to stainless rails. 3) Cage length is adjustable but must not be shorter than 2/3 of the total rail length. Available lengths 1) L mm Maximum rail length mm L L L L L L L L L 200 l l l l l l l l l l l l l 400 L L L L L L 400 l l l l l l l 400 L L l 400 Available lengths 1) Maximum rail length L mm mm L L L L L L L L L 400 1) Other rail lengths are available on request but new J 1 dimension has to be calculated as described in chapter 3.1.7, Calculation of J 1 dimension. l) Prompt delivery L) Delivery time on request 63

64 Ball and crossed roller assemblies D w t 1 t t 3 D w t 1 t t 3 t 2 U LWJK 2 ACSM LWAKE 4 ACSM D w t 1 t t 2 t 3 LWAKE 3, 6, 9 ACSM Designation Dimensions Load ratings for 10 rolling elements dynamic static D w t t 1 t 2 t 3 C 10 C 0 10 Maximum cage length 1) Appropriate rail guide mm N Balls/mm LWJK 2 ACSM 2 3,9 1,5 0 3, balls LWRB 2 ACSM LWAKE 3 ACSM 4 6,25 2,65 3, LWRE 3 ACSM, LWRE 2211 ACSM LWAKE 4 ACSM 6,5 8 4,3 4, LWRE 4 ACSM LWAKE 6 ACSM LWRE 6 ACSM LWAKE 9 ACSM ,35 8,65 21, LWRE 9 ACSM 1) Longer cages are available on request. 64

65 2.5 LWRM / LWRV Rail guides Needle roller assemblies End pieces LWRM/LWRV rail guides offer guiding systems with high load carrying capacity and maximum rigidity. The mounting and interface dimensions of LWRM/LWRV rail guides conform to those of all the SKF Modular Range rail guides included in this catalogue. LWHW needle roller assemblies have aluminium cages with retained needle rollers. LWHV needle roller assemblies consist of a plastic cage with retained needle rollers. They are available for size 6 and 9 units. When ordering, the appropriate cage length in mm should be stated after the cage designation, e.g.: LWHW 10x225. End pieces serve to prevent the drift of the cage away from the loaded zone. Because of the design of LWRM/LWRV rail guides and the respective end pieces, only one rail, the M-shaped or the V-shaped, has to be equipped with end pieces. LWEARM and LWEARV end pieces feature a plastic wiper with a sealing lip that keeps the raceways virtually free from contamination. All end pieces are supplied with appropriate mounting screws. 2 Ordering example: 2x LWRM x LWRV x LWHW 15x358 4x LWERM 9 65

66 LWRM / LWRV precision rail guides A 2 J 3 D w G 1 A 1 N G J 2 J 4 B B N 1 N 1 A J 5 J 6 J 2 G N G 1 A 3 LWRM LWRV G 3 G 2 LWRM J 1 J J 1 L Designation 1) Dimensions Weight Mounting holes End face holes A B A 1 A 2 A 3 D w J J 1 J 1 min J 2 G G 1 N N 1 J 3 J 4 J 5 J 6 G 2 G 3 mm kg/m mm mm mm mm LWRM ,5 2 1, M 6 5,2 9,5 5,2 8,5 7 M 3 6 LWRV ,8 10,8 2 1, M 6 5,2 9,5 5,2 7 6 M 3 6 LWRM ,1 2 3, M 8 6,8 10,5 6, M 5 8 LWRV ,9 16,6 2 3, M 8 6,8 10,5 6, M 5 8 1) Sizes LWRM/LWRV 12 and 15 are available on request. 66

67 2 G 3 G 2 LWRV J 1 J J 1 L Available lengths 1) L mm Maximum rail length mm l l l l l L l L L L l l l l l L l L L L l l l l L L L L L l l l l l l L L L ) Other rail lengths are available on request but new J 1 dimension has to be calculated as described in chapter 3.1.7, Calculation of J 1 dimension. l) Prompt delivery L) Delivery time on request 67

68 Needle roller assemblies U D w t U D w t LWHV L w t 1 plastic LWHW L w t 1 aluminium Designation Dimensions Load ratings for a cage with 2 rows of 10 needles dynamic static D w L w U t t 1 C 10 C 0 10 Maximum cage length Appropriate rail guide mm N mm LWHV ,8 10 3,75 2, LWRM 6/LWRV 6 LWHW ,8 10 3,75 2, LWRM 6/LWRV 6 LWHV ,8 15 3,75 2, LWRM 9/LWRV 9 LWHW ,8 15 4,5 3, LWRM 9/LWRV 9 LWRM / LWRV end pieces L L 1 L L 1 wiper wiper LWERM LWEARM LWERV LWEARV Designation Dimensions Attachment screw Appropriate rail End pieces End pieces DIN 7984 guide with wiper L L 1 mm LWERM 6 4 M 3 LWRM 6 LWERV 6 4 M 3 LWRV 6 LWEARM 6 6 M 3 LWRM 6 LWEARV 6 6 M 3 LWRV 6 LWERM 9 6,5 M 5 LWRM 9 LWERV 9 6,5 M 5 LWRV 9 LWEARM 9 8,5 M 5 LWRM 9 LWEARV 9 8,5 M 5 LWRV 9 68

69 2.6 LWM / LWV Rail guides LWM/LWV rail guides enable linear guiding systems to be designed for heavy loads and with maximum rigidity. The internal geometry is identical with that of the Modular Range rails of the LWRM/LWRV series. As the same needle roller assembly is used, the load ratings are also the same. The external dimensions of the LWM/ LWV rail guides differ slightly from those of the LWRM/LWRV Modular Range dimensions. LWM/LWV rail guides are widely used, especially in the machine tool industry. As standard, they are supplied with mounting holes of type 15 (through hole with counter bore). If attachment hole type 13 is ordered, corresponding threaded inserts are supplied with the guide. Hole type 03, directly-machined thread with dimension G, is available on request. For new designs, LWRM/LWRV rail guides are recommended, and offer the advantage of being interchangeable with other rail guides of the Modular Range. Needle roller assemblies LWHW needle roller assemblies comprise an aluminium cage with needle rollers arranged at right angles to each other. The needle rollers are retained by the cage. LWHV needle roller assemblies, consisting of a plastic cage with retained needle rollers, are available in size LWHV15 and LWHV20. End pieces for LWM/LWV rail guides End pieces serve to prevent drift of the cage away from the loaded zone. Because of the design of LWM/LWV rail guides and the respective end pieces, only one rail, the M-shaped or the V-shaped, has to be equipped with end pieces. LWEAM and LWEAV end pieces have the addition of a plastic wiper with a sealing lip that keeps the raceway virtually free of dirt. All end pieces are supplied together with mounting screws. Ordering example 2x LWM x LWV x LWHW 15x130 4x LWEM

70 LWM / LWV precision rail guides D w A 1 N J 3 J 2 N2 J 4 B N 1 B N 1 A J 5 J 6 N 2 N LWM Hole type 15 A 2 A 3 J 2 LWV Hole type 15 G 3 G 2 LWM J 1 J J 1 L Designation Dimensions Weight Mounting holes End face holes A B A 1 A 2 A 3 D w J 1) J 1 min 2) J 2 G N N 1 N 2 J 3 J 4 J 5 J 6 G 2 G 3 mm kg/m mm mm mm mm LWM , ,5 M 4 8,5 4,5 5, M 3 6 LWV ,2 10,5 2 1, ,5 M 4 8,5 4,5 5,25 7 5,5 M 3 6 LWM ,3 2 2, ,5 M 6 11,5 6,8 7, M 5 7 LWV ,5 2 2, ,5 M 6 11,5 6,8 7,5 10,5 5,5 M 5 7 LWM , M 6 11,5 6,8 7, M 6 8 LWV , M 6 11,5 6,8 7, M 6 8 LWM ,5 7, M M 6 8 LWV ,5 7, M M 6 8 LWM , M 10 18, , M 6 8 LWV , M 10 18, , M 6 8 LWM ,5 13, M M 6 8 LWV ,5 26 3,5 14, M M 6 8 1) For lengths L < J+2 J 1min : J = 50 mm (except for LWM/LWV 3015) 2) J 1 = (L J) / 2 70

71 G 2 G LWM Hole type 13 LWV Hole type 13 G 3 G 2 LWV J 1 J J 1 L Available lengths 1) L mm Maximum rail length mm l2) l l l l L L l2) l l l l L L l l l l l L L L L L L l l l l l L L L L L L l l l l l L L L L L l l l l l L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L ) Other rail lengths available on request 2) J = 35 mm l) Prompt delivery L) Delivery time on request 71

72 Needle roller assemblies U D w t U D w t LWHV L w t 1 plastic LWHW L w t 1 aluminium Designation Dimensions Load ratings for a cage with 2 rows of 10 needles dynamic static D w L w U t t 1 C 10 C 0 10 Maximum cage length Appropriate rail guide mm N mm LWHV ,8 10 3,75 2, LWM/LWV 3015 LWHW ,8 10 3,75 2, LWM/LWV 3015 LWHV ,8 15 3,75 2, LWM/LWV LWHW ,8 15 4,5 3, LWM/LWV LWHV 20 2,5 11, , LWM/LWV 6035 LWHW 20 2,5 9,8 20 5, LWM/LWV 6035 LWHW , , LWM/LWV 7040 LWHW 30 3,5 17, LWM/LWV 8050 LWM / LWV end pieces L L 1 wiper L L 1 wiper LWEM LWEAM LWEV LWEAV Designation Dimensions Attachment screw Appropriate rail End pieces End pieces DIN 7984 guide with wiper L L 1 mm LWEM M 3 LWM 3015 LWEV M 3 LWV 3015 LWEAM M 3 LWM 3015 LWEAV M 3 LWV 3015 LWEM ,5 M 5 LWM 4020 LWEV ,5 M 5 LWV 4020 LWEAM ,5 M 5 LWM 4020 LWEAV ,5 M 5 LWV 4020 LWEM/LWEV 5025 to M 6 LWM / LWV 5025 to 8050 LWEAM/LWEAV 5025 to M 6 LWM / LWV 5025 to

73 2.7 LWM / LWV ACSZ Rail guides Needle roller assemblies End pieces LWM / LWV ACSZ rail guides are identical to LWM / LWV rail guides, but designed for use with anti-creeping LWHW ACSZ cages. For this purpose, both rails are equipped with gear racks made of steel. The cage carries two steel control gears that are always in mesh with the racks during operation, and help to ensure the right cage position. As standard, the rails are prepared for maximum stroke, with gear racks over the full rail length ( chapter 1.4). In principle, LWHW ACSZ are the same as LWHW cages, whereby LWHW ACSZ needle roller cages incorporate two steel control gears located at the centre of the cage. The load carrying capacity of LWHW ACSZ cages is also identical with that of LWHW standard cages. ACSZ does not result in additional cage length. LWHW ACSZ needle roller assemblies comprise an aluminium cage with retained needle rollers. Generally, end pieces are not needed for LWM / LWV ACSZ rail guides, since cagecreeping is prevented by the ACSZ. For production reasons, the tapped holes on the rail s end face are standard, and most end pieces, as for LWM / LWV rail guides, can be used with the exception of LWEAV. If tapped holes on the end face are not required, the rails should be ordered with option E1. Ordering example 2x LWM ACSZ 2x LWV ACSZ 2x LWHW 20x220 ACSZ 2 73

74 LWM / LWV ACSZ precision rail guides D w A 1 N J 3 J 2 N 2 J 4 B N 1 B N 1 A J 5 J 6 N 2 N A 2 A 3 J 2 LWM ACSZ Hole type 15 LWV ACSZ Hole type 15 G 3 G 2 LWM ACSZ J 1 J J 1 L Designation Dimensions Weight Mounting holes End face holes A B A 1 A 2 A 3 D w J 1) J 1 min 2) J 2 G N N 1 N 2 J 3 J 4 J 5 J 6 G 2 G 3 mm kg/m mm mm mm mm LWM 3015 ACSZ , ,5 M 4 8,5 4,5 5, M 3 6 LWV 3015 ACSZ ,2 10,5 2 1, ,5 M 4 8,5 4,5 5,25 7 5,5 M 3 6 LWM 4020 ACSZ ,3 2 2, ,5 M 6 11,5 6,8 7, M 5 7 LWV 4020 ACSZ ,5 2 2, ,5 M 6 11,5 6,8 7,5 10,5 5,5 M 5 7 LWM 5025 ACSZ , M 6 11,5 6,8 7, M 6 8 LWV 5025 ACSZ , M 6 11,5 6,8 7, M 6 8 LWM 6035 ACSZ ,5 7, M M 6 8 LWV 6035 ACSZ ,5 7, M M 6 8 LWM 7040 ACSZ , M 10 18, , M 6 8 LWV 7040 ACSZ , M 10 18, , M 6 8 LWM 8050 ACSZ ,5 13, M M 6 8 LWV 8050 ACSZ ,5 26 3,5 14, M M 6 8 1) For lengths L < J+2 J 1min : J = 50 mm (except for LWM/LWV 3015) 2) J 1 = (L J) / 2 74

75 G 2 G LWM ACSZ Hole type 13 LWV ACSZ Hole type 13 G 3 G 2 LWV ACSZ J 1 J J 1 L Available lengths 1) L mm Maximum rail length mm L2) L L L L L L L2) L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L ) Other rail lengths available on request 2) J = 35 mm l) Prompt delivery L) Delivery time on request 75

76 Needle roller assemblies U D w t L w LWHW ACSZ t 1 Designation Dimensions Load ratings for a cage with 2 rows of 10 needles dynamic static D w L w U t t 1 C 10 C 0 10 Maximum cage length Appropriate rail guide mm N mm LWHW 10 ACSZ 2 4,8 10 3,75 2, LWM/LWV 3015 ACSZ LWHW 15 ACSZ 2 6,8 15 4,5 3, LWM/LWV ACSZ LWHW 20 ACSZ 2,5 9,8 20 5, LWM/LWV 6035 ACSZ LWHW 25 ACSZ 3 13, , LWM/LWV 7040 ACSZ LWHW 30 ACSZ 3,5 17, LWM/LWV 8050 ACSZ LWM / LWV ACSZ end pieces L L 1 wiper L L 1 wiper LWEM LWEAM LWEV LWEAV Designation Dimensions Attachment screw Appropriate rail End pieces End pieces DIN 7984 guide with wiper L L 1 mm LWEM M 3 LWM 3015 ACSZ LWEV M 3 LWV 3015 ACSZ LWEAM M 3 LWM 3015 ACSZ LWEM ,5 M 5 LWM 4020 ACSZ LWEV ,5 M 5 LWV 4020 ACSZ LWEAM ,5 M 5 LWM 4020 ACSZ LWEM/LWEV 5025 to M 6 LWM / LWV 5025 to 8050 ACSZ LWEAM 5025 to M 6 LWM / LWV 5025 to 8050 ACSZ 76

77 2.8 LWRPM / LWRPV Rail guides LWRPM/LWRPV rail guides are linear guides for limited travel, fitted with Turcite-B slide coating. Based on PTFE, this material is self-lubricating and offers excellent sliding properties. The coating is bonded to the non-hardened LWRPM rail and subsequently ground to size. Separate ordering of the slide coating is not required. The LWRPV rail is hardened and ground. In order to avoid damage to the sliding surface of the LWRPM rail, the LWRPV rail has a lead-in radius as standard. LWRPM/LWRPV rail guides should be used where rail guides with rolling element assemblies are unsuitable due to external influences, for example, extremely short strokes, high impact loads or dusty environment. The mounting and interface dimensions of the LWRPM/LWRPV rail guides conform to those of all the SKF Modular Range rail guides included in this catalogue. More details can be found in chapter Technical data of precision rail guides with slide coating. LWRPM/LWRPV rail guides are characterised by: Stick-slip-free operation. Smooth running. Good emergency running properties. Low wear and high reliability. Resistance to contamination. Excellent vibration damping properties. End pieces LWRPM/LWRPV rail guides normally do not require end pieces. For this reason, tapped holes on the end faces are also unnecessary. However, for production reasons, LWRPV rail guides will, in certain cases, be supplied with tapped holes. Ordering example: 2 LWRPM LWRPV 6300 LWRPM / LWRPV Slide coating Designation 1) Dimensions Load Rail guide capacity 2) H C mm N / 100 mm LWRPM 3 0,7 300 LWRPM 6 1,7 700 LWRPM 9 1, ) The slide coating is an integral part of the LWRPM rail and does not have to be ordered separately. 2) For a surface loading of approx. 1 N/mm 2 (momentary loads of up to 6 N/mm 2 are permissible). H 2 77

78 LWRPM / LWRPV precision rail guides A 2 H J 2 N A 1 G 1 G B N 1 B N 1 A G N G 1 A 3 J 2 LWRPM LWRPV J 1 J J 1 L LWRPM Designation 1) Dimensions Weight Mounting holes A B A 1 A 2 A 3 J J 1 J 1 min J 2 G G 1 N N 1 mm kg/m mm mm LWRPM ,5 0, ,5 5 3,5 M 4 3,3 6 3,2 LWRPV ,6 6,45 0, ,5 5 3,5 M 4 3,3 6 3,2 LWRPM ,6 1, M 6 5,2 9,5 5,2 LWRPV ,8 10,8 1, M 6 5,2 9,5 5,2 LWRPM ,1 3, M 8 6,8 10,5 6,2 LWRPV ,9 16,6 3, M 8 6,8 10,5 6,2 1) Sizes LWRPM/LWRPV 12 and LWRPM/LWRPV 15 are available on request. 78

79 2 J 1 J J 1 L LWRPV Available lengths 1) L mm Maximum rail length mm l l l l l l l L L L L 400 l l l l l l l L L L L 400 L l l l l l L L L L L L L L l l l l l L l L L L L L L l l l l L L L L L l l l L L L L L L ) Other rail lengths are available on request but new J 1 dimension has to be calculated as described in chapter 3.1.7, Calculation of J 1 dimension. l) Prompt delivery L) Delivery time on request 79

80 2.9 Other products Besides the standard product range, on request SKF can offer additional cages and guiding types, such as flat rail guides or wrap-around guidings. Also, completely customized guidings can be manufactured for applications that do not allow the use of standard products LWML / LWV The LWML rail guide consists of a modified LWM rail guide with the addition of an integrated adjustment wedge ( chapter , fig. 6). Used in conjunction with an LWV guide and a needle roller assembly, this provides a preload-adjustable guide system. Inclination of the wedge surface is 1,5%, so that a displacement of the wedge by 1 mm brings about a 15 µm alteration in the height. LWML rail guides are available in classes P10 and P5. When ordering, it should be specified whether the preloading threads are right-hand or left-hand threads LWN / LWO LWN/LWO rail guides differ from the LWM/LWV rail guides only in height, width and attachment holes. The internal geometry of the two rail guide series is the same and their load ratings are identical. LWN/LWO rail guides are available in precision classes P10, P5 and P LWJ / LWS flat rail guides LWJ/LWS flat rail guides are used in conjunction with LWRM/LWRV, LWM/LWV or LWN/LWO rail guides as non-locating linear guides. They are incorporated in floating slides. LWJ/LWS flat rail guides, as well as the appropriate rolling element assemblies and end pieces, are available on request. Customised guidings With the knowledge and manufacturing capabilities existing within SKF, it is possible for SKF to produce completely customized guidings or other precision parts. 80

81 2.10 GCL / GCLA standard slides GCL and GCLA are pre-assembled slides made of steel or aluminium, and crossed roller precision rail guides for applications that require maximum accuracy and rigidity. Typical applications are factory automation, printing, packaging and general machinery. GCL and GCLA standard slides are available on request. 2 Advantages: Top and base plate of a GCL are made of blackened steel or cast iron (depending on size) or aluminium for GCLA. Standard patterns of attachment holes for easy mounting. Upper and lower mounting surfaces are ground for high running accuracy. Reference edge parallel to the slide axis (opposite of preload set screws). Internal end stops to limit the stroke. Very low friction of the rail guides. Relubrication identical with precision rail guides, ( chapter 3.3). GCL / GCLA data Guidings: GCL / GCLA 2 LWRB 2 with LWJK 2 GCL / GCLA 3 LWR 3 with LWAK 3 GCL / GCLA 6 LWR 6 with LWAL 6 GCL / GCLA 9 LWR 9 with LWAL 9 Optional with anti creeping solution ACS/ACSM and / or coating Operating temperature 30 to +80 C Maximum speed 2 m/s Maximum acceleration 25 m/s 2 Friction coefficient 0,003 0,005 (with normal, light lubrication) Preload Preloaded in factory with standard values Precision class P10 (other precision class on request) Lubrication Lightly greased on assembly Optional customized solutions possible LGCL / GCLA running accuracy GCL Stroke (mm) Straightness height T z 2 mm 2 mm 3 mm 3 mm 4 mm Straightness side T y 2 mm 2 mm 2 mm 3 mm 3 mm GCLA Stroke (mm) Straightness height T z 4 mm 4 mm 6 mm 7 mm 8 mm Straightness side T y 4 mm 4 mm 5 mm 6 mm 7 mm 81

82 GCL D w T N S/2 J 1 n J J 1 S/2 H B 1 J 2 J 6 G B N 1 H H 3 L 1 H 2 Designation 1) Dimensions 0,2 ±0,1 Stroke 2) 0,4 B H L S 1 S 2 B 1 D w G H 1 H 2 H 3 n J J 1 J 2 mm mm GCL M ,5 15 GCL GCL GCL GCL GCL GCL GCL M4 9 18, ,5 25 GCL GCL GCL GCL GCL GCL GCL M , GCL GCL GCL GCL GCL GCL M , GCL GCL GCL ) Delivery time generally on request 2) S 1 standard stroke order designation, e.g. GCL 2060, S 2 extended stroke order designation, e.g. GCL 2060/L 3) Take chapter 1.7.2, in consideration. 82

83 J 7 J 7 J 8 B J 6 B J 6 Fig. 1 L Fig. 2 L 2 J 7 J 8 J 7 J 8 J 9 B J 6 B J 6 Fig. 3 Fig. 4 L L Effective dynamic load capacity of the slide Effective static load capacity of the slide 3) with S 1 with S 2 with S 1 with S 2 Weight J 6 J 7 J 8 J 9 Fig N N 1 T C eff slide C 0 eff slide mm N N kg , , , , , , , ,5 8 4, , , , , , ,6 11 6, , , , , , , , , , ,3 83

84 GCLA D w T N S/2 J 1 n J J 1 S/2 H B 1 J 2 J 6 G B N 1 H H 3 L 1 H 2 Designation 1) Dimensions 0,2 ±0,1 Stroke 2) 0,4 B H L S 1 S 2 B 1 D w G H 1 H 2 H 3 n J J 1 J 2 mm mm GCLA M ,5 15 GCLA GCLA GCLA GCLA GCLA GCLA GCLA M4 9 18, ,5 25 GCLA GCLA GCLA GCLA GCLA GCLA GCLA M , GCLA GCLA GCLA GCLA GCLA GCLA M , GCLA GCLA GCLA ) Delivery time generally on request 2) S 1 standard stroke order designation, e.g. GCLA 2060, S 2 extended stroke order designation, e.g. GCLA 2060/L 3) Take chapter 1.7.2, in consideration. 84

85 J 7 J 7 J 8 B J 6 B J 6 Fig. 1 L Fig. 2 L 2 J 7 J 8 J 7 J 8 J 9 B J 6 B J 6 Fig. 3 Fig. 4 L L Effective dynamic load capacity of the slide Effective static load capacity of the slide 3) with S 1 with S 2 with S 1 with S 2 Weight J 6 J 7 J 8 J 9 Fig N N 1 T C eff slide C 0 eff slide mm N N kg , , , , , , , ,5 8 4, , , , , , , , ,6 11 6, , , , , , , , ,2 85

86 2.11 LZM miniature slide With the LZM miniature slide product range, SKF offers the ideal solution for linear motion applications with short strokes and compact boundary dimensions. The use of miniature slides has significantly increased in medical applications, measurement technologies and micro mechanics and assembly. The various LZM miniature slide components are designed to meet the highest precision standards. LZM miniature slides feature high running accuracy and smooth motion, and are manufactured with allstainless-steel components. The maximum value for parallelism between the raceways and the mounting surface is 3 µm. Optimized hardness enables long service life and high performance within compact boundary dimensions. Ease of installation is another positive feature of LZM miniature slides. Unlike crossed roller systems using 4 rails and 2 cages to be assembled on the production floor, the LZM miniature slide provides a complete slide that can simply be bolted into place without the use of precision devices to set preload. Customized miniature slides are also possible, and SKF will modify existing designs to meet specific technical requirements. Wide versions of LZMs for higher torque loads can also be supplied on request. Wide versions of LZMs for higher torque loads, comparable with wide miniature profile rail guides LLMWS, can also be supplied on request. Applications: Pneumatics Semi-conductor manufacturing Medical Micro- and electronics assembly Measurement applications Fibre optics Advantages: Compact design High load capacity Very good running accuracy Smooth running High rigidity Easy assembly Ordering example LZMHS 9 26 (P5, T0 as standard no need to specify) LZMHS 9 26 T2 P1 86